Henshin tells the story of Junichi, a young boy who is forced to go through a life-saving brain transplantation. By his side, his girlfriend Kei is watching over him all the time. Junichi seems to recover complete from this operation, but while Kei is thrilled that he is back by her side, Junichi senses that all is not well. Something inside of him seems to have changed and his feelings for Kei are beginning to fade. Though he wants nothing more than for the two of them to be happily together, Junichi realizes that something must be done. He makes a bold decision to protect the young woman he loves that will prove to everybody, especially himself, what his true feelings for Kei really are.