Yuichi Kudo is a male honor student excelling academically in Okitsu High School's Class 2A, yet he struggles profoundly with self-control concerning his romantic feelings for classmate Kenta Suetake. Openly gay, Yuichi harbors an intense infatuation with Suetake, who remains completely oblivious despite the affections being glaringly obvious to their classmates. This unreciprocated passion triggers extreme physical reactions, most notably recurrent nosebleeds portrayed as signs of sexual arousal. These episodes reach such severity that they occasionally cause him to lose consciousness, necessitating medical intervention. His peers have consequently dubbed him "the nosebleed king."

Yuichi frequently indulges in fantasies about Suetake but actively pursues real interactions, such as offering tutoring sessions. While the entire class, including teacher Mika Suzuki, recognizes Yuichi's feelings and reacts with eye-rolling or exasperation—mirroring their response to Rio Kitagawa's open pursuit of Mika-sensei—Suetake himself remains entirely ignorant of Yuichi's romantic intentions. Unlike Mika-sensei, who is aware of Kitagawa's feelings, Suetake perceives nothing.

Innocent comments or actions from Suetake easily provoke Yuichi's volatile emotional responses, often resulting in exaggerated nosebleeds that underscore his characterization as governed by emotion rather than rationality. His infatuation serves as a recurring source of humor within the class dynamic while simultaneously highlighting his vulnerability. His romantic pursuit shows no significant evolution or resolution across the series or extended media. Details regarding his family background, external interests, or personal history remain unspecified.

Yuichi's role centers on the juxtaposition of his academic diligence against his comedic lack of restraint regarding Suetake. His interactions are largely confined to this dynamic, without substantial development or exploration of deeper personal conflicts in the available material. The narrative consistently frames his sexuality and romantic fixation as defining traits, without delving into broader aspects of his identity or relationships outside this unrequited love.