Seven years after the battle with Cell, Gohan is now a high school student attending Orange Star High School.

As Videl is called in to stop a bus hijacking, Gohan, using the alias "Great Saiyaman", pitches in to help the passengers while Videl handles the criminals. The next day, Gohan learns that Chobi, the child of Toto the pterodactyl, has been captured by a circus and put on display. In his attempt to rescue Chobi, Gohan is portrayed as a criminal and is pursued by Videl. However, when Chobi's parents attack the city in search of their child, Gohan manages to handle the situation and return Chobi to his parents. Later, Videl, who discovers the truth that Gohan is Great Saiyaman, blackmails him into participating in the 25th World Martial Arts Tournament. As some of the other Z Fighters express interest in the tournament, Goku calls out from the Other World, saying he will return to Earth for a single day to particpate.

After Gohan spreads word of the tournament to the others, as well as managing to convince Chi-Chi to let him participate himself, Gohan takes a leave of absence from school and begins training with Goten. Gohan is surprised to find that Goten not only possesses great strength, but is also already capable of transforming into a Super Saiyan, although he has yet to learn how to fly. Later, Videl comes around to have Gohan make good on his promise to teach her how to fly using bukū-jutsu, with Gohan starting her off with the basics of learning how to control her energy. Within a day, Videl has managed to learn how to float while Goten has managed to learn how to fly. Following a remark from Gohan, Videl comes back the next day with her hair cut, determined to learn more from Gohan. Meanwhile, Vegeta is also surprised to find that Trunks is also capable of becoming a Super Saiyan, whose strength is slightly higher than Goten's, while Goku trains fiercely in anticipation for the tournament.

After ten days of training, Videl manages to master flight, finally giving Gohan and Goten the opportunity to resume their training for the tournament. On the day of the tournament, Gohan suggests to Vegeta, Goten, and Trunks that they don't use their Super Saiyan forms during the tournament to avoid hassle from the press. Arriving at the island where the tournament will take place, Gohan and the others are greeted by Goku, who the fortune teller Baba has granted 24 hours to stay on Earth, allowing him to meet Goten for the first time, while Piccolo destroys all the cameras in the area to keep Gohan's identity a secret. After the participating fighters register for the tournament, with Goten and Trunks forced to participate in the junior division, the preliminary rounds begin, where the fighters must hit a punching machine to rank their strength, with the Dragon Team effortlessly qualifying.

While Gohan and Videl wait to take their preliminaries, Goku, Vegeta, and the others go to spectate the junior division, where Goten and Trunks effortlessly progress through each round until they face each other in the final round. The battle gets more and more intense, with Goten and Trunks surprising the audience with advanced techniques and even turning Super Saiyan. The match eventually comes to an end where a sneak attack by Trunks causing Goten to lose by ring-out. Satan, who had spectated the fight and had been reminded of the battle with Cell, now faces a pinch as he now has to fight against Trunks.

After various attempts to try and get out of the fight, Satan decides to pretend to lose and have Trunks hold back his attack in order to keep up his appearance, though even Trunks' weakest punch manages to send Satan flying. During an intermission, Trunks and Goten decide to take out one of the participants and steal his clothes in order take his place in the adult division. Meanwhile, as Goku and the others get something to eat, they encounter a pair of mysterious participants, Shin and Kibito, who Piccolo determine as not being from Earth. As the sixteen qualifying participants gather together to decide the drawings for the first round, Gohan is paired up against Kibito while Goku gets paired up against Vegeta.

As the drawings come to a close, Piccolo is put up against Shin while #18 is up against Satan. After Krillin wins his first match against his opponent, Piccolo and Shin face against each other, but as Piccolo senses an overwhelming power coming from Shin, he decides to forfeit the match before it even begins, feeling Shin's power is far beyond his own. As Videl prepares to go up against a man named Spopovitch, Piccolo learns from Kibito that Shin is actually the Supreme Kai, believed to be even more powerful than the Grand Kai. Videl appears to get the upper hand in her match, but Spopovitch keeps getting up no matter how many times he is knocked down and eventually fights back. Goku suspects something amiss about Spopovitch, which proves true when he continues fighting even after Videl breaks his neck. Videl attempts to use her flight to regain her strength, but Spopovitch follows her into the air and uses energy blasts against her. As Videl refuses to give up despite the beating she is taking, Goku wonders where Spopovitch got his power from.

With Spopovich nearly beating Videl to death, Gohan loses his temper and prepares to storm onto the field, but Spopovich's partner, Yamu, convinces Spopovich to end the fight by pushing Videl out of the ring. With Videl heavily injured, Goku uses his instant transmission to receive some senzu beans from Korin, which Gohan gives to Videl to restore her to full health. Gohan, whose identity is revealed to his classmates after his bandana was blown off during his outburst, steps up to face against Kibito, who requests to see Gohan's Super Saiyan transformation. After Piccolo informs the other Z-Fighters of Shin's identity as the Supreme Kai, he orders Gohan to transform. Right after Gohan transforms, Spopovich and Yamu appear and use a device to drain his Super Saiyan energy, leaving him weakened. As Kibito offers to tend to Gohan, the Supreme Kai asks Goku and the others to join him in pursuing the culprits.

As Goku and the others set off to join the Supreme Kai, Kibito uses his unique ability to restore Gohan's energy, before the two of them, along with Videl, set off after the others. Along the way, Supreme Kai and Kibito explain to the others about how an evil mage named Babidi is seeking to revive an evil being known as Majin Buu, who was responsible for the death of four Supreme Kais long ago. To accomplish this, he manipulated Spopovich and Yamu to join the tournament and steal Super Saiyan energy needed to break the seal placed on Buu. Unable to push her flight any further, Videl, coming to understand that Gohan was the one who defeated Cell back then, places her faith in him and returns to the tournament grounds, while Gohan and Kibito catch up to Goku's group. Arriving at the site of a buried spaceship, the Z-Fighters lay in watch as Spopovich and Yamu deliver Gohan's energy to Babidi and his partner, Dabura, the Demon King.

Supreme Kai and Kibito warn Goku and the others about the malicious pair, with Dabura being the strongest being of the underworld and Babidi possessing magic powerful enough to sway him to become his henchman. Having obtained the energy from them and deeming them of no further use, Babidi kills Spopovich with his magic while having his other henchman, Pui Pui, kill Yamu. Having detected the presence of the Z-Fighters, Babidi and Pui Pui head inside of the ship while Dabura attacks the group, immediately killing Kibito and firing his spit at Krillin and Piccolo, turning them into stone. Learning that they can only unpetrify them by killing Dabura, the remaining fighters chase after him into the ship, despite Supreme Kai's warnings. Upon reaching the first floor, they are confronted by Pui Pui, who informs them they must face several floors before they can reach Babidi at the bottom. The Saiyans, however, don't think much of their opponent and play a game of rock-paper-scissors to decide who should fight him, with Vegeta stepping up against him.

As Vegeta easily outmatches Pui Pui in terms of fighting skill, Babidi changes the stage to match that of the high gravity planet, Zun, where Pui Pui is at his top fighting form. However, this makes no difference to Vegeta, who obliterates his opponent and opens the way to the next floor. Believing the Saiyans to not be underestimated, Babidi sends in his next warrior, Yakon, and changes the stage to that of Planet Ankoku, but even with the aid of pitch black darkness, Yakon is no match for Goku's keen senses. When Goku turns Super Saiyan, however, Yakon uses his ability to consume light and sucks in Goku's energy, turning him back into normal. Rather than finding an alternative way to fight, Goku instead feeds him even more Saiyan energy until he explodes from being overloaded, allowing Goku and the others to move onto the next stage.

As Babidi fears the power of the Saiyans, Dabura decides to face them himself, going inside a meditation chamber to raise his power before his battle. Meanwhile, back at the tournament, Goten and Trunks take a break from their Mighty Mask disguise to get some drinks, barely avoiding having their cover blown. With Goku and the other members still missing, Satan suggests that a battle royale be held between the remaining contestants; #18, "Mighty Mask", Killa, Jewel, and himself. As the match begins, Killa and Jewel are quickly dispatched by #18 and the Trunks/Goten combo, who proceed to ignore Satan and go after each other.

As the battle between #18 and "Mighty Mask" continues to escalate, #18 struggles to keep up with her opponent's unpredictable moves, but manages to land a critical hit against the pair, knocking them into the center of the stage. Goten and Trunks decide to switch places with Goten now on top, pushing #18 to the point where she starts using energy blasts against them, but she manages to hit back with support from her child. The pair decide to go Super Saiyan and launch a powerful blast at #18, but she manages to dodge it and reveal their true identity, resulting in the pair becoming disqualified, leaving #18 and Satan as the only remaining fighters. As Goten and Trunks come across Videl upon her return, Dabura emerges from his meditation chamber, ready to face off against Gohan.

Noticing his complete lack of fighting skill, #18 makes a deal with Satan to let him win the match and maintain his dignity in exchange for twice the price money. Meanwhile, Goten and Trunks, having heard about the current situation from Videl, become interested and head towards the action. Back at the spaceship, Dabura appears before Gohan, deciding to give him a handicap by choosing an arena similar to Earth's environment. As the fight gets underway, both Gohan and Dabura bring out their full power against each other. Despite being hit by some of Dabura's powerful attacks, Gohan refuses to lose against him.

As the battle between Gohan and Dabura continues, Vegeta's impatience to settle things with Goku catches the attention of Dabura, who decides to abandon the fight and report to Babidi. Learning that Vegeta still retains a lot of evil in his heart, Babidi uses his magic to target Vegeta's mind and sway him over to his side. To make matters worse, Babidi transports everyone to the tournament grounds, where Vegeta, still focused on his desire to defeat Goku, prepares to face off against him even with innocent bystanders watching.

Vegeta begins his attack on Goku, killing several innocent people in the crowd without any remorse. Realising Vegeta had fallen under Babidi's spell on purpose purely for the sake of his grudge, Goku is left with no choice but to fight against him, despite Supreme Kai's attempt to stop him, and has Babidi warp them to somewhere they can fight alone. As Supreme Kai and Gohan decide to go on ahead and leave the two Saiyans to their fight, Babidi attempts to command Vegeta to kill them, but his pride defies even his master's demands.

While Goku and Vegeta's fight gets underway, building energy for Majin Buu each time Goku takes damage, Gohan and Supreme Kai arrive at Majin Buu's egg, where they are confronted by Babidi and Dabura. Before the fight between them can begin, Majin Buu's egg reaches full power as a result of Goku and Vegeta's battle.

Goku and Vegeta's fight continues to escalate, with Vegeta revealing he chose to go under Babidi's control in order to gain the strength to face against Goku, feeling he needed to get rid of his gentle side. Meanwhile, as the seal containing Majin Buu starts to be break, Gohan attempts to stop him reaching full power by shooting multiple Kamehameha Waves at the egg. The egg splits apart with seemingly nothing more than pink smoke coming out of it, leading Supreme Kai to presume Majin Buu had been destroyed. However, Gohan senses a powerful energy from the smoke, which forms together to make Majin Buu, who appears to be nothing more than a mere child.

Everyone seems to be bewildered by Buu's childlike behavior, curious as to whether his rebirth was actually unsuccessful. However, Buu soon shows off his frightening strength when he effortlessly beats Dabura, the rise in his power level even catching the attention of the other Saiyans. Although Goku tries to convince Vegeta to postpone the fight in order to stop Buu, Vegeta knocks out Goku when he drops his guard, taking a senzu bean and setting off to fight Buu himself. Gohan and Supreme Kai attempt to flee from Buu, but he easily catches up to them, proving himself immune to Supreme Kai's attacks.

Buu completely overwhelms Supreme Kai and Gohan, with Supreme Kai using the last of his strength to make sure Gohan survives Buu's attack. Before Buu can finish Supreme Kai, he is attacked by Dabura, who believes he cannot be made to obey anyone. Meanwhile, Goten and Trunks arrive nearby, inadvertently breaking the petrified Piccolo. Unfazed by Dabura's attacks, Buu uses his unique ability to turn Dabura into a cookie and eats him, undoing the petrification on Krillin and Piccolo, the latter of whom survived being broken thanks to his regenerative abilities. Before Buu can do the same to Supreme Kai, Vegeta arrives on the scene.

Vegeta, willing to put his life on the line, begins his assault on Buu, managing to blast a hole through him. However, Buu manages to regenerate himself and builds up his anger to create a giant explosion, dealing heavy damage to Vegeta.

As Vegeta is ensnared by Buu, Trunks and Goten can no longer stand by, and rush to the scene to rescue him, while Piccolo attacks the defenseless Babidi and rips him to pieces. Feeling he cannot defeat Buu with conventional means, Vegeta says his farewells to Trunks before knocking both children out, instructing Piccolo to take them far away. Once everyone is clear from the scene, Vegeta uses his last resort, overloading his Super Saiyan for and sacrificing himself in a massive self-destructive explosion in order to obliterate Buu.

As Bulma and the others from the stadium follow Videl's directions in pursuit of Goten and Trunks, they are hit by the shockwave from Vegeta's attack and almost crash, but are saved by #18. Piccolo leaves Goten and Trunks with Krillin, telling him to inform the others that Vegeta and possibly Gohan have been killed, before he investigates the site of Vegeta's sacrificial attack, finding various charred fragments of Buu, along with Babidi, who narrowly survived the explosion. However, Piccolo is shocked to witness Buu's fragments suddenly come to life and reassemble to bring Buu back to his normal form. As Buu uses his power to heal Babidi, who vows to make the planet suffer, Piccolo decides to take Goten and Trunks up to Kami's tower. Elsewhere, Goku regains conciousness and tries to determine the situation, while a weakened Supreme Kai searches for Gohan, whose fate is still unknown.

Bulma's group goes to seek out the Dragon Balls so they can revive all the spectators that Vegeta killed, coming up against a large dragon whilst trying to get the last one. Meanwhile, as Piccolo and Krillin as they leave Goten and Trunks in the care of Dende and Mr. Popo, they are soon joined by Goku, who learns about the situation. Goku states he isn't strong enough to defeat Buu, but mentions having learned a technique known as Fusion, in which two similarly built fighters can merge together to become a single powerful fighter. Though he had originally planned to do this himself with either Gohan or Vegeta, Goku realises from Mr. Popo that he can instead teach this technique to Goten and Trunks, due to their similar size.

Using the Dragon Balls, Bulma summons out Shenron, using one of its wishes to bring back everyone who had been killed that day. As using all three wishes would mean they would have to wait another year before they can use the Dragon Balls again, Goku warps over to Bulma's group and convinces Shenron to postpone the other two wishes, shortening that time to four months. Kibito, who was revived by the wish, manages to find Supreme Kai and heal his injuries, and together they manage to find Gohan and decide to bring him to the world of the Kais. Meanwhile, Goku warps Bulma and the others to Kami's Palace, where he informs them of the grim situation concerning Gohan and Vegeta, before Babidi announces his message to the world.

Speaking to the people of Earth, Babidi threatens far-reaching destruction unless Piccolo, Goten, and Trunks reveal themselves. Despite this, Goku endeavours to teach Fusion to the boys. Meanwhile, Gohan is taken to the sacred domain of the Supreme Kais, and returned to fitness by Kibito, but can he draw the Z-Sword from its resting place?

Despite the protestations of others at Kami's Lookout, Videl continues to believe that Gohan survived his fight with Majin Buu. As it happens, Gohan, both alive and well, draws out the legendary Z-Sword, and, believing that it will be the key to victory, begins training with it. Babidi and Majin Buu continue their tour of destruction, and receive some important information.

Realizing that Majin Buu is headed for Capsule Corp., Trunks breaks off from his Fusion training, and heads home to retrieve the Dragon Radar. To buy him the time he needs, Goku engages Majin Buu, and showcases a new level of power. Far away from the fighting, Mr. Satan pledges to save the people of Earth from Majin Buu.

Trunks arrives at Capsule Corp., and hurries to find the Dragon Radar, although his grandparents seem unconcerned with the danger they are in. Meanwhile, Goku desperately tries to delay Majin Buu, and learns first-hand the terrifying power that Buu possesses. Enticed by the promise of an even greater opponent than Goku, Buu begins to question his subservience to Babidi.

Free from Babidi's control, Buu heads off on a rampage. Goku reveals that, as a result of his Super Saiyan 3 transformation during his fight with Buu, he has less than one hour left on Earth. Betting everything on Goten and Trunks, Goku shows them the Fusion Pose, but it turns out to be an embarrassing dance.

Goten and Trunks are bored of fusion training and ask Goku to show them Super Saiyan 3. However, doing this causes him to use up what was left of his little time on Earth. Now he must say goodbye, once more.

Gohan begins training with the Kai’s. Majin Buu runs rampant. Just when Gohan gets a handle on the sword…it breaks?!

Old Kai decides to draw out Gohan’s potential, but the process is a long one. Gohan and Trunks finally complete their fusion: Gotenks!

An overly confident fused Gotenks, searches for Buu, however he is unsuccessful. Mr. Satan approaches Buu?

Old Kai helps Gohan to unlock his inner strength, Goten and Trunks successfully fuse in Super Saiyan form. Majin Buu inadvertently befriends a puppy after healing its injured leg.

Mr. Satan is able to calm Buu after telling him the dog is still alive. Mr. Satan gets shot and Buu loses it!

Born from within, Buu is separated into good and evil. Evil Buu defeats and eats Good Buu, from which Super Buu is born! He goes off in search of Gotenks, who still isn’t ready. Can Piccolo stall?

Super Buu unleashes an attack on the Earth, but is managed to get stalled for another hour. Gohan grows impatient with Old Kai.

Piccolo barely manages to stall Super Buu, who is now on his way to challenge Goten and Trunks in the Hyperbolic Time Chamber.

Gotenks immediately shows off new moves against Super Buu. While mostly ineffective, Gotenks eventually uses the Super Ghost Kamikaze Attack that destroys Super Buu! Or does it…?

Piccolo destroys the entrance to the Hyperbolic Time Chamber, trapping himself, Goten, Trunks, and Super Buu inside…forever! Super Buu lets off a dimension ripping scream! Gotenks shows off Super Saiyan 3!

Gotenks and Piccolo manage to escape the Hyperbolic Time Chamber and challenge Super Buu. A back-and-forth battle continues!

Gotenks fusion time is nearly up and his power is waning. As Super Buu moves in, a newly powered up Gohan arrives.

Gohan immensely overwhelms Buu with his new power. Super Buu attempts to self-destruct to take Gohan with him, but is unsuccessful. What will he do next?

Playing on Gohan’s over-confidence, Super Buu challenges Gotenks and uses the ploy to absorb Gotenks and Piccolo. Super Buu gains the advantage over Gohan.

With Gohan struggling, the Other World makes strides towards sending Goku and Vegeta back to Earth. Old Kai gives up his life, for Goku.

Armed with fusion earrings, Goku goes to the battle and attempts to fuse with Gohan. One of the earrings gets lost and Super Buu manages to absorb Gohan. With no one to fuse with, Vegeta arrives. Can Goku convince him to fuse?

A reluctant Vegeta and Goku fuse, and a new super fighter is born! Vegito! Instantly holding the upper hand, Super Buu makes a desperate move – entering Vegito’s body and attempting to control him from within.

Vegito manages to dispel Super Buu from his body. Super Buu manages to turn him into candy, but even Candy Vegito is still stronger. Utilizing a piece of himself from the battlefield, Super Buu manages to surprise Vegito and absorb him.

Vegito willingly was absorbed and placed a shield over himself before being absorbed. Inside, Goku and Vegeta de-fuse, mysteriously, and search for the others. With all the fighters removed, what will happen to Super Buu’s form?

Instead of weakening after the loss of those he absorbed, Original (Kid) Buu is powered up and stronger than ever!

Old Kai explains Majin Buu’s origins. The new Kid Buu decides to try his powers out…on the entire Earth!

Kid Buu follows the fighters to the world of the Kai’s. He begins his destruction by attacking Grand Kai’s planet. Kid Buu located Goku and Vegeta, who plays rock, paper, scissors to see who goes first. Goku is up

Goku powers up to Super Saiyan 3 and continues to fight Kid Buu. As Vegeta observes the fights, he reminisces of his fights with Goku.

Kid Buu is still too powerful. Goku steps aside and offers the battle to Vegeta, who declines, knowing he is no match. Goku has used up all his power.

After Vegeta attempts to stall for Goku, he is on the verge of death. Can Goku power up in time? Fat Buu enters the fight and manages to stall for a little time. Goku has one last idea.

Having the Namekian dragon wish back the Earth and all of its people, Goku attempts one final attack. The Spirit Bomb!

Vegeta pleads with the people of the Earth to give Goku energy. None of the fighters pleas make it through…except for one, Mr. Satan steps in and the Earth begins to pour in energy.

Goku fires the Spirit Bomb at Kid Buu, who attempts to fight it. Vegeta makes the final wish from Porunga to restore Goku to full power. At long last, Majin Buu is final defeated!

10 years have passed since the defeat of Majin Buu. The World Tournament is upon the fighters and there is a new human with the potential to defeat Goku and Vegeta?

Uub is strong, but has no fighting experience. Goku decides to take it upon himself to train with Uub, hoping one day his power will be strong enough to fight him. Goku and Uub say farewell, and fly off into the distance…