Sumire Kasahara

Kasahara is one of the girls who bully Nishimura. She's a part of a friend grop that constitutes the more relentless of the female bullies in the class.

She used to run competitively in sports when she was younger, but seems to have lost interest in showing that side of her. She's also very fond of kittens.

[Spoiler] A bit later, she developed a crush on Takada. She is also the first (and so far only) girl who starts contemplating her role as Nishimura's bully and turns over a new leaf by tentatively trying to become her friend instead. [/Spoiler]