In a future governed through the lens of a camera, where people eat synthetic food and pursue an online existence in lieu of physical contact, a group of children begin meeting up in the real world. The aloof Ayumi Kono, the genius hacker Mio Tsuzuki, and the socially awkward Hazuki Makino set out to find the fourth member of their group, Yuko Yabe, who has gone missing. With the help of Myao Rei, an unregistered citizen proficient in martial arts, they are able to find Yuko. However, when their situation takes a sudden turn for the worse, the group stumbles headlong into a dark mystery that challenges everything they know about their world.

This is an OVA released on October 27th, 2006. It is also classified as the 13th episode (thus a sequel) to Kashimashi ~Girl Meets Girl~. Hazumu confessed his love to Yasuna, but she turned him down him. To ease his heartbreak, he went to Mt. Kashimayama where he had met her first. However he lost his way in the mountain, and it was night time. He saw a big shooting star, and when he began to wish, he found out that something was wrong. It was not a shooting star, but it was a falling space ship. He was involved in the crash, but he managed to survive by the help of an alien. However, he became a girl due to the accident during the reconstruction of his body.

A world blanketed in an endless and ever-growing ocean of snow. The people eke out a living, either huddled around the roots of enormous trees dotting the surface, or high in the canopy, which spreads over the planet's atmosphere. A chance meeting between Kaina, a youth from the canopy, and Liliha, a young woman from the surface, sets off a chain of events that will change the fate of the world.

The Urusei Yatsura story comes to a climax in this animated retelling of the final Manga story (although not the final movie). Lupa, yet another one of Lum's fiancés, arrives on the scene, and Lum and Ataru have to repeat their game of tag in order to prevent the Earth from being destroyed.

All Ataru has to do to win is say "I love you" the three words he has steadfastly refused to say to Lum. Will he admit his true feelings and save the Earth? Or will his pride doom it to destruction?

(Source: AniDB)