Hiroyuki, otherwise referred to as Yuki, is a tall and attractive transsexual woman in a relationship with her boyfriend Shii. Yuki takes an early interest in Yoshino when she believes him to be a cis boy, though remains on good terms with him even after learning of his assigned sex. Yuki sees a lot of herself in Shuuichi, though there are several major differences between their situations. When Yuki was growing up, Shii was the only friend who stood by her while the girls would tease her, and the boys would bully her to change.

Yuki dislikes cooking anything, though she runs a gay bar. She always keeps up a positive attitude, and can easily understand what Shuuichi and Yoshino are going through; as such, she is often able to give helpful advice when they are troubled. Her parents run a uniform store, and as she has not been on good terms with her family since her transition, it has been a long time since she has been to her former home.

In the Takako Shimura's short story collection Boku wa, Onna no ko, Yuki is the main character of the story "Hana." Yuki's family—which consists of her father, mother, brother, and sister-in-law—appears here, and Yuki is revealed to be a fan of Keiji Sata, a Showa period actor.