On Tokyo Jupiter, a 17yr old boy, name Ayato, is living a normal life until, Tokyo Jupiter is attacked. When Ayato is saved by Haruka, Ayato cracks an egg which released a structure, known as RahXephon, to fight against Mu.

Itsuki finds a stone, while examining the Dolem that was defeated in the prior episode. Itsuki takes that stone and gives it as a gift to Sayoko, for Christmas. After, he goes to the beach and invites Ayato, Megu, and Haruka and the others to a Christmas Eve Party. And it begins to snow. While Megu and Kim are shopping Megu talks about Haruka, while Haruka gives Ayato gloves. And a Dolem appears to freeze everything. And RahXephon and Ayato must defeat it, but there's a problem, Sayoko is a part of it. And it's up to Ayato to save christmas for Nirai Kanai. When it looks in doubt, Ayato thinks of Haruka and the gloves he gave her, and saves the day.

B-Storyline: Quon stays in bed under her blanket, because she hates the snow.

A dolem is beating RahXephon, and Ayato is writhing on the floor of the cockpit, and is in a dream state where, Toyko is much different, there are flashes of a Murian, Mamoru, Hiroko, Haruka Mishima and his mother.

Megu is going through a test to become a full-fledged member of TERRA. Ayato is still depressed because he's a Mulian and everyone was keeping it from him. He's going around biting people's heads off, accusing them of laughing about him behind his back. Haruka is worried about telling Ayato some secret. The two of them talk. Haruka says that it doesn't matter that Ayato is a Mulian, but he doesn't listen. Sayoko breaks it off with Iishiki, saying that he was using her, but she was also using him. She gives him a dress as a token, because she no longer has anyone to wear it for. And Quon is about to be moved to her new home. Megu passes her test and she is going to meet someone to tell him about her feelings for him. But when she goes to meet him, she finds that Souichi is already in a relationship with Kim. She's upset at first, but Kim starts to cry, so Megu forgives her. Quon asks Ayato to take her to Tokyo and he agrees, flying off in the RahXephon.

Eager to prove himself, Ishiki fires Haruka over a trivial matter and takes control of the attack on Tokyo Jupiter. Against orders, he moves the attack up one hour. The attack commences with disastrous results.

Meanwhile, Ayato is busy finishing up his painting when he receives a call from Kunugi to pick up Mamoru's cat. While there, he learns how Haruka saved him from the concentration camps. Returning home, he finishes his painting. He is about to show Haruka when Mishima appears and reveals her true purpose for her existence and Ayato's destiny with the RahXephon.

The RahXephon has transformed into its final state and the battle between the Xephons has begun. The outcome will not only determine the fate of Ayato and his loved ones but also the world.