Minori Izumi befriends protagonist Mayuki Hyuga when he starts school, quickly developing an infatuation with him. Her interactions frequently feature a rivalry with classmate Yae Yatomi (Yaya) as they compete for Mayuki's attention, a dynamic central to her role.

She has an older sister, Sanae Izumi, who regularly joins Mayuki and his friends on adventures. Later revelations show Sanae is one of two "dolls" controlled by Mayuki's butler, Seiran Shinano; this discovery doesn't change Minori's position or relationships. Minori remains an ordinary schoolgirl, uninvolved with the supernatural mysteries surrounding the Hyuga family and focused on everyday social dynamics.