Despite being a first year in high school, Yuuki is very child-like. She seems to be obsessed with Nodoka's large breasts and wants larger ones herself. She is flirtatious towards Kyoutarou; whether this is because of an actual attraction or because she likes to poke fun is unknown. She is also protective of her friends: during the nationals when the media says that the Nagano prefecture has been dropping in power, she gets angry because she feels that they are making fun of her friends and she vows to make them pay.
She is also quite prideful, as Nodoka noted that she wouldn't let herself cry in front of other first-years, but was willing to cry when only Mako and Hisa were in the room.