Hayato Ninomiya is a student at Mitsu Higashi High School, attending class 2-A and serving as a key member of the school's rowing club. As the only male member of the club, he specializes in the single scull, a racing shell designed for a single rower, which distinguishes his role from the team-oriented boats typically used by other members.

Within the school, Ninomiya carries a reputation as a genuine boat fanatic, known for being constantly absorbed in thoughts about rowing to the point that his dedication borders on obsession. This singular focus on the sport defines much of his personality and daily life, marking him as someone deeply passionate about the technical and physical aspects of rowing. When new members, including a girl named Etsuko, express interest in joining the club, Ninomiya welcomes them warmly and takes on the responsibility of teaching them the basic skills and techniques required for rowing. This willingness to instruct newcomers demonstrates a patient and helpful side, balancing his reputation as a mere enthusiast with the practical role of a mentor and club leader. His position as the solitary male member also places him in a unique dynamic within the team, often surrounded by female club members whom he helps guide in the sport. While his abilities are clearly centered on the single scull, his most notable trait is his unwavering dedication to rowing, which serves as the primary motivation for his actions throughout the story. As the narrative progresses, his role remains that of a foundational pillar for the club, providing both expertise and encouragement to the developing rowers around him, though specific details of his personal growth remain closely tied to his consistent passion for the sport.