A 24-year-old office worker named Sasaki decides to join a local gym, hoping to break free from a monotonous routine and improve her overall health. During her visits, she meets her personal trainer, a cool and charismatic older woman named Sora Gorōmaru. Sasaki affectionately refers to her as Oneesan, or big sister. Rather than a strict instructor, Gorōmaru is deeply invested in her client's progress, offering enthusiastic encouragement and emotional support that goes beyond standard fitness advice.

The core of the narrative revolves around the unique dynamic that develops between the pair during their training sessions. Gorōmaru uses unconventional motivational methods, including suggestive or risqué situations presented as rewards for Sasaki's hard work. This approach blends elements of comedy, lighthearted romance, and slice-of-life storytelling, with the chemistry between the dedicated pupil and her playful mentor serving as the main focal point. Through this relationship, the story explores themes of personal growth, building self-confidence, and finding connection in everyday life.

The manga was serialized on Kodansha's Comic Days app, beginning in August 2023, and its storyline concluded in May 2025. The final compiled book volume was published shortly after, bringing Sasaki and Sora Gorōmaru's fitness journey to a close.