Yukimi Yasuda attends Seishū High School as both a student and track club member. She previously attended a different middle school, where she developed a crush on Katsuya Niimi. After transferring to Seishū at the start of the school year, she pursued him relentlessly, causing tension with the more reserved Yuri Nakao due to their shared feelings for him.

Yukimi contrasts Yuri's timid nature through her loud, outspoken, confident, and demanding personality. She expertly leverages her feminine charms, offering dates or promises of physical affection like kisses to influence male peers. Despite her assertive independence, her core objective centers on winning Katsuya's love and securing marriage. She supports him through actions such as cooking meals and leading cheers.

During the characters' third year, Yukimi's romantic arc resolves with Jirō Yamanaka—Seishū baseball team's third baseman and younger brother of Katsuya's former rival, Kentarō. Jirō had long nurtured a crush on Yukimi since joining the team. This shift occurs alongside the baseball team's pursuit of the Kōshien championships.

Her family background remains undefined except for a theatrical movie cameo by her grandmother. Her narrative concludes without elaboration on her athletic involvement or relationships beyond her romantic resolution with Jirō.