Birthday: November 7
Weight: 38.33 KG (OVA 7)
Height: 145 cm

Riko is the younger twin sister. A way to tell her apart from Ako is that she wears her hair in a ponytail, and it is longer than her sister's hair. Also, she has a bandage below her left eye. She has a habit of answering truthfully but very bluntly, causing everyone else to jump to conclusions, even at one time about to honestly state that she and her sister wanted a computer solely for porn, however was quickly stopped by Ako. She is much shyer in person than her sister, as she could not kiss Keita in front of others. At school, she is on the disciplinary committee, where she uses a bokken/shinai to punish the students and she has more of a strict personality, yet just like her sister will abuse her authority to get Keita.