Shidou Shion

Hobbies: Playing competitive fighting games
Likes: Intense battles that get her blood pumping, kimonos, Japanese swords
Dislikes: Half-assed or badly incorporated battles, people who have talent but don't use it, pervy jokes

Toshiki's classmate who is good at writing the battle genre. Despite her cold outlook, she is quite kind. For some reason, she has been regarding Toshiki as her rival ever since they became classmates.
She is also Yuuma's twin sister and claims to be the older one.

Based on the official website