Rein Tsunomoto  

, 角元 れいん

Rein uses cards as her weapon, having grown up with Sayumiya. The Hida family took her in after her father disappeared. She enjoys card games and gambling due to her familiarity with handling them. Rein is also fond of words and often speaks using one word while splitting it into three parts that all mean the same thing, such as when she referred to Sayumiya as an "idiot," a "moron," and a "dingdong." Her maternal side is evident when an abandoned baby arrives at the Gokujou Seitokais dormitory. This may be due to her father abandoning her when she was young, making her understand how it feels not to be loved by anyone. Pucchan sometimes calls her "little-kid senpai" because of her childish behavior and nature. Rein also cheats frequently in order to avoid losing (consecutive losses mean separation).