Hirai functions as butler and caretaker for wealthy student Kyle Matsutake, meticulously attending to his young master's daily needs and personal welfare with unwavering dedication. His role demands complete dependence on Kyle's preferences and instructions, resulting in Hirai organizing his entire existence around fulfilling Kyle's requirements.

He maintains a professional relationship with Hoshino, butler to Momo Umezono. Although their employers' competing affections for Kyle and Katie suggest potential rivalry, their interactions display moments of mutual understanding and an underlying rapport that transcends mere professional competition.

Hirai debuted in Episode 9. His portrayal remains consistent across all documented media, focusing exclusively on his service to Kyle; his motivations, personal history, and character evolution remain largely unexplored.