Antonina Antonovna Nikitina

Tonya is Soushichi’s classmate and also a member of the student council. Being a Russian exchange student, she possesses silky silver hair and has a slightly more minute stature than the average. On the outside, an innocent(?) school girl but really she is a

Spoiler

secret agent from Russia investigating in Jinyous of Japan

.
Tonya possesses a calm, witty, analytical side

Spoiler

that compliments her job as a spy

but also her snarky, playful and mischievous nature makes her a very rounded character. It’s probably not an exaggeration that most of her sharky side is in her fights with Suzu (i.e. always). But how she teases Soushichi and Keijirou/Io about their romantic relation, her anger/jealous mode when someone tries to "advise" on her physique, in contrast to how she is always a reliable ally in combat and her kindness that is shown indirectly makes me think she is the best support any protagonist can get.