Just before summer break, Sakuta encounters Shouko Makinohara, a girl in junior high with the same name and face as his first love. Of course, that should be impossible, since she would be in college by now. Then, as if one mystery wasn't bad enough, Adolescence Syndrome strikes again. His impassive friend from the science club, Rio, discovers she has a doppelg nger. One of the Rios is forced out of her house and winds up staying at Sakuta's apartment...