Ushimaru Yuki is a student at Morinomiya Academy in the same class with Kashima Ryuuichi and Kamitani Hayato.
Yuki is a teenage girl below average height with an ample bust with a brown bob hairstyle. She is seen by the male classmates as a cute and endearing person.
Yuki is a popular girl and tends to draw the attention of the male students because of her cute looks and gentle personality.
While she is kind-hearted and soft-spoken, she is also painfully shy and often gets embarrassed when interacting with her crush, Ryuuichi. She often gets confused and uneasy when dealing with small children.
Ushimaru develops a crush on Ryuuichi, having seen his dedication towards taking care of his brother, Kotarou. However, Ryuuichi is seen as viewing her only as a normal girl contrary to the other male students in class. Her infatuation with Ryuuichi leads her to be acquainted with Inomata Maria who also shares the same feelings. Even though they do not acknowledge each other outright as rivals, they eventually go on to become close friends. Ushimaru teaches Inomata on social skills and the importance of forming a bond with her classmates.
Due to her negative experiences with children flipping her skirt or generally getting harassed by them in the past, she has a phobia of interacting with the daycare children initially. On Inomata's prodding and persuasion, she agrees to try befriending the daycare children and is well-received by Kirin and the rest of them. She finds Kotarou to be well-behaved and surprisingly "cute" after walking with him for awhile, attributing it to his similarities with his brother whom she likes. However, things took a wrong turn as she overthinks the situation and with Taka tugging on her skirt accidentally to wipe Kotaro's nose and Kirin giving her an innocent gift of bugs. This causes her to faint out of shock. Nevertheless, the children show up at the infirmary with wild flowers to apologize afterwards and she learns that their playfulness are in fact a way of getting to know her.
- Ushi from Ushimaru, means "cow" or "ox".
- Yuki is more tone deaf than Inomata, but she still wants to go for karaoke with her someday.