小太刀 凪

Kyoutarou's neighbor. She likes to eat snacks often and watching TV while making misleading actions that leaves Kyoutarou very confused. While she likes going to other people's rooms, she won't allow anyone enter hers, saying that a girl's room is filled with secrets. Although Nagi is a very casual person, sometimes she will say something cool. People think she is a fearless girl but deep down, she is afraid of animals.

She is actually the one who uses magic for Kyoutarou to experience the Library Club with so many girls, thus implying all of them have actually been forced to join. She is also his childhood friend, and at the same time, his younger step-sister.