Hiroyuki is a supporting character from the anime HEN. He is an adult male with red hair that reaches chest length and gray eyes. He works as a singer in a band and is noted for having a dark or gothic stage appearance, with the tags of singer and idol associated with his character.

In the story, Hiroyuki is initially involved in a purely physical relationship with the protagonist Chizuru Yoshira, a relationship that lacks any romantic feelings from either side. Both characters claim not to understand or believe in love, treating their connection as one of convenience rather than emotion. Hiroyuki’s motivations shift after a conversation with Chizuru about the nature of love. Following a concert that Chizuru attends with her friends, Hiroyuki leaves with another girl. When Chizuru discovers them together in his apartment, she remains unperturbed and declares she will never return. It is at this moment that Hiroyuki follows her and declares his love, begging her not to leave him, suggesting that the preceding conversation made him realize his own feelings are the opposite of what he claimed.

Later in the narrative, a new character named Azumi Yamada enters the scene. As Chizuru begins to develop confusing feelings of attraction toward Azumi, Hiroyuki becomes jealous. His response is to attempt to seduce Azumi himself, with the stated goal of taking her virginity in order to spite Chizuru and cause her disappointment. This action positions Hiroyuki as a complicating factor in the central relationship of the story.

No notable special abilities are attributed to Hiroyuki beyond his musical talent as a singer. His personality is characterized by emotional detachment early on, shifting to possessiveness and jealousy as the plot progresses, and ultimately revealing a cruel and manipulative streak in his efforts to interfere with Chizuru's emerging feelings for Azumi.