Saegusa Yukika

A female student in Class 2-A.
The track girl trio's mascot, she is patient and mature.
She admires her classmate Tohsaka Rin, for reasons that have nothing to do with her being an honors student.
She has many younger brothers, and though her family is poor, her heart is rich.
Her smile is soothing, and her rabbit-like warmth makes people want to take care of her.
It seems she actually wanted to join the cooking club, but was strong-armed into becoming the track team's manager by Makidera Kaede.
As you might expect, she's exceptionally nonathletic.

Fate/side material: Fate Encyclopedia