They are Yatora's classmate who invited Yatora to join the art club.

Yuka is boisterous and seemingly confident, despite their underlying anxieties. They act in a cutesy and flamboyant manner which tends to attract a lot of people to them.

They are closest to their grandmother, who is the reason why they decided to pursue Japanese Art. Yuka will often put on a bright demeanor in front of them, and when placed in stressful situations they are often brash and impulsive.

(Source: Blue Period Wiki)