Rena attends the same grade as Keiichi, but she is a few months younger than him. Her birthday falls in July, and since nearly all of the arcs take place before July 1983, Rena has not yet turned 14.

Rena has an obsession with all things cute. In what the others call her "Cute Mode" (かぁいい・Kāii), she often tries to take such things home in her Take Home (お持ち帰り・omochikaeri) Mode even if they do not belong to her. Such things include the "Kenta-kun" doll, Furude Rika, Hanyū, Satoko, and any of the club members in cute punishment game outfits. She spends much of her time "treasure hunting" at the town's trash heap in search of cute things which often appeal only to her. In the trash heap, Rena has a secret base consisting of an old van she has filled with things she likes to which she retreats when distressed. Nevertheless, according to Mion, while Rena might seem cute herself, people should be careful not to anger her as she can become quite scary. Keiichi discovers this in an infamous scene in the Sound Novels, manga, and anime where she suddenly screams "Lie (嘘だ・うそだ・usoda)!"