Sora fell from the roof of his high school and was knocked unconscious. When he finally awoke, he found a kind-hearted boy named Sunao waiting over him. Sunao claims to be his best friend, but the fall erased some of Sora's memory. He doesn't remember Sunao at all, the wide-eyed young man acts like much more than just a friend. From that day on, Sora begins to experience flashbacks in which he is not himself, but a mysterious alternate personality with hidden powers. He begins to search for the secret of his lost memory and the flashbacks, but will Sunao be his companion, or his enemy?