Kouno Sayaka

The daughter of Toru's aunt and uncle that adopted him, making her Toru's younger step-sister and cousin. She is in love with Toru and is very adamant (to the point of psychosis) about them getting married one day, against the wishes of Toru himself (as his feelings for her never evolved beyond that for a sister). She is overly obsessive with him and has hurt one of Toru's previous girlfriends by shoving her down a set of steps out of jealousy.