Hozumi, a gifted scientist, is researching human cloning to save his beautiful and dying fiance, Hiroko. However, just before the completion of the project, Hozumi suddenly quits the lab, to stay with Hiroko until her last moment. Doesn't he want to save his fiance? Fellow scientists are puzzled by Hozumi's course of action and wants him back on the research team, but Muto, an ambitious scientist sees an opportunity to take over the cloning research.

Kirihara's life was full of lies and loneliness. He was a picture book writer with a brilliant past that his first book hit a bestseller, but one day allegations of plagiarism of his first book emerged. The truth of the case was about to be revealed by a reporter who relentlessly chased after him. Around that time, he reunited with his mother, who had abandoned himself at an early age, but she was hospitalized unconscious. Despaired by his life, Kirihara jumps off the roof of the building and tries to commit suicide without improving his divorced relationship with his wife and son. A girl appears there to help him. The moment he thought "Who?!", Kirihara became the girl! Kirihara, who became the girl, witnesses him falling. Immediately after that, something even more mysterious happens. The time was back five days ago. This is how the mysterious five days of "Two Kirihara", a girl and a picture book writer, begins...