Junichi Naruse, an average guy with a passion for art, decides to pursue drawing and painting again. Upon doing so, he meets and falls in love with Megumi Hamura. After they start dating and eventually make the decision to live together, Junichi visits a real estate office. However, while attempting to save a child during a robbery, he is shot in the head.

Regaining consciousness a month after the incident, Junichi's miraculous recovery is made possible by receiving a brain transplant from an unknown donor. As time passes, Junichi notices drastic changes to his personality, affecting his relationships as he struggles to maintain them. Gradually approaching the brink of insanity, he attempts to figure out the cause by determining who the donor is before losing sight of his own identity forever.