- Voice Actor (CV)
- Misuzu Togashi
- Role
- Supporting
- Identity
- A high-achieving middle school student who shares a classroom with protagonist Tomoya Mizuhara and happens to be the younger brother of Ruri Hayasaka
Personality
Meticulous and disciplined
Academically exceptional
Secret sister complex
Frequent target of teasing
Kouki Hayasaka serves as one of the key supporting characters in the series, appearing as a trusted friend and classmate of the main protagonist. Known throughout school for his disciplined nature and consistently top-ranking grades, he projects an air of maturity—yet conceals a soft spot for his sister Ruri, despite her rough treatment of him. His overly earnest personality and tendency to take everything at face value make him an easy mark for the female cast's pranks, casting him as an endearing comedic foil in the story's lighthearted everyday moments.