Rein uses playing cards as her weapon and is a childhood friend of Sayuri. The Hida family took her in after her father disappeared. She enjoys playing card games and does not mind gambling, due to her familiarity with handling cards. Rein also has a love of words, and many times, she is heard speaking a sentence using one word and splitting it three ways though they all mean the same thing, such as when she called Sayuri "an idiot, a moron, and a complete dingdong". Rein has an extremely maternal side that is shown when an abandoned baby turns up at the Gokujou Seitokai's dormitory. This is said to be due to the fact that her father abandoned her when she was very young, making her understand well how it feels to not be loved by anyone. Sometimes Pucchan oftenly refers her as "little-kid-senpai" due to her childish acts and nature. Rein also cheats quite a lot because she doesn't want to lose (consecutive losses means separation).

[Wikipedia]