Baseball-kun, also known as Yakyuu-bu-kun, is a high school baseball team member and the childhood friend turned romantic partner of Cheer-chan. Their relationship starts with shared childhood familiarity but shifts during adolescence as Baseball-kun grows conscious of Cheer-chan's physical appeal and her rise to popularity as a model following media attention. This transforms his view of her from friend to romantic interest.

Their bond fits the classic "Jock and Cheerleader" dynamic, rooted in their school roles and shared experiences. The narrative highlights his perspective navigating Cheer-chan's sudden fame and the admiration she attracts, especially after her appearance as a cheerleader during a nationally televised baseball game draws widespread notice. His feelings for her are genuine and reciprocated, though her newfound status introduces complexity.

Physically, he possesses a typical baseball player's athletic build and often wears a buzz-cut hairstyle fitting his high school athlete identity. While his specific family background and detailed personality traits appear without elaboration, his role centers on his emotional connection to Cheer-chan and his reactions to her changing social standing. Their story underscores themes of young romance complicated by external factors like sudden fame and societal expectations.

The character features primarily in the anime's second season, specifically in episodes 8, 10, and 12, plus the first OVA. These appearances focus on his interactions with Cheer-chan and their evolving relationship amid her modeling career.