Itoshi no Nina

One afternoon, Atsushi's best friend from childhood, Masa, informs him, "I kidnapped Niina Aota." Niina, whose popular nickname is Nina, is the girl Masa fell in love with at first sight on the train attending school. Atsushi found it unexpected and hard to believe, until he heads over to Masa's apartment and discovers that Nina has really been kidnapped.... (Source: MyAnimeList)