Yotsuba Mitsuru, the day before his 17th birthday, is dumped for the 30th time. Remembering a promise with his best friend, who shared his birthdate, made 10 years before, he goes to the park to meet him, when a flash of light knocks him out just as he thinks he sees his friend. He awakens in the hospital and discovers he's been given a second chance at life... with a few strings attached.