Takeru has been telling Ryou what ideal woman would be like, when suddenly a bright light zooms down out of the sky, hits a tree, and BAM! Who should appear in the tree but Takeru's ideal woman, naked as a jaybird? She seems very vulnerable and scared and obviously doesn't know the basics of human customs or even speech. Takeru gives her a name and vows to protect her.

Takeru and Hikari explain to his friends and family what happened the previous night. Hikari tells them she came to Earth from outer space because she was lonely, but doesn't know anything else about herself. However, because Takeru saved her he's now very precious to her. Takeru's male classmates go wild with jealousy because he's got a cute babe now.

Ryou is waiting to meet someone, although he himself doesn't really know this until he meets her. Her name is Akari, and she is obviously similar to Hikari in that she doesn't remember her past or have a name. Akari is living in the forest, because she remembers being there when she saw a night where there was a very bright light, and she wants to see a night like that again. Ryou begins going to see her regularly on his walks home, and begins to feel very protective towards her.

Ryou takes Akari home with him and soon his little sister Kimi starts to grow fond of Akari in spite of herself, and the three wind up declaring themselves a family, after which Akari moves into the Ninomiya household. Akari is introduced to Hikari and learns that she too came from space. Jennifer suggests that they used to be one being with no body, and then divided into two and gained bodies after they got to Earth.

Hikaru thinks it will be enjoyable to go to school with Takeru so she begins school with him. Soon she finds out that it is really boring.

It's summer break, and they all go to the mountains to camp. Hikari and Akari learn about nature and are happy; Ioneous and Jennifer get drunk, and are also happy. The group decides to play a game in the dark where they're basically supposed to split up into pairs and stake a flag on a rock. Hikari and Takeru wind up together and the rest of the group has fun spying on them, until Ioneous in monster-form starts running around in a drunken fit, making them think they're being attacked.

After the mountains, everyone heads to the beach. They all pitch in to help Takeru's aunt and uncle's beach restaurant. With Hikari making so many mistakes, she and Takeru are allowed to take off. They are attacked by a huge water dragon like thing and Takeru turns into his suped up form to save her.

It is the time for the Festival of Lanterns where Japanese people honor their dead. Hikari wonders about death and it's reality is presented to her when a cricket she's been keeping dies. Jennifer reports on the ED (Extended Definition) phenomena to her superiors. They wonder about what is to happen with a new extinction on the way, something that's happened seven times before in Earth's history. Hikari is plagued by dreams in which her "dark" half wonders why she's fraternizing with those she's to destroy.

Takeru gets a fixer upper bike and spends most of his time working on it. Hikari feels left out and Mari takes the whole gang to a junk yard to find parts for the motorcycle. At the junk yard Akari confronts Hikari about their roles on Earth while Ryou and Takeru talk about their new found powers in the garage.

Mari buys a present for Takeru and is going to tell him her feelings for him. When she get to the garage, she sees Takeru about to kiss Hikari. She gets mad at Hikari and slaps her which triggers the destroyer in her. Now things are set in motion for the Earth to be cleansed for the next wave of evolution.

Hikari shows Takeru why he doesn't really love her and why he cannot truly love. Jennifer tells everyone her theories about what Hikari is and Ioneous confirms it. Ryou and Akari arrive trying to stop Hikari. Ryou shows Takeru why they are different even though they both have had parents that abandonded them.

Takeru convinces Hikari that he loves her, for real this time. Things have already been set in motion by Ioneous though so they must stop him before it's too late for the Earth.