Chiyo Iin (伊い院いん 知ち与よ, Īn Chiyo?), is a character in The 100 Girlfriends Who Really, Really, Really, Really, Really Love You. She is originally introduced as Rentarou's stepcousin and later become his 12th girlfriend. She is a third-year student at Ohananomitsu High School, in class 1-1, and serves as class president. Chiyo values tidiness and order. She gets frustrated when she sees anything that is disorganized and is compelled to intervene and fix them. Chiyo lost her mother at a young age, and was raised solely by her father (and Rentarou's stepuncle) Hiro. Despite liking the compliments for being responsible at first, Chiyo secretly feels burdened by these high expectations. Chiyo is prone to breaking down when she loses her glasses. While Rentarou had reservations about entering a relationship with his stepcousin, partly due to his stepuncle interfering in events to get them closer, he accepted after she honestly confessed to him.