TV-Series
Description
Ichirō Satō, a 17-year-old third-year student at Kawanuma West High School, sports short brown hair and dark blue eyes. He consistently wears the school uniform: a short-sleeved collared white shirt, blue tie, light grey pants, and blue sneakers. Academically, he maintains average scores of "3" across every subject—Japanese, social studies, math, science, music, art, physical education, home economics, and foreign language—placing him among the lowest-ranked students in his class.

During a childhood Christmas visit to his mother’s hometown, Satō jumped into a river believing it would hasten his transition to adulthood. A shy teenage girl, later revealed to be his future teacher Kana Kojima, rescued him. They bathed together at her house, where he discovered his first pubic hair and insisted on verifying hers to confirm their shared "adulthood." Though Satō initially forgot the incident, it profoundly impacted Kojima, influencing her career choice and her initial stern teaching persona, dubbed "Kojima the Demon."

Satō frequently encounters Kojima in embarrassing and erotic situations across locations like restrooms, bathhouses, pools, and the school infirmary. These escalate through contrived coincidences, misunderstandings, or botched resolutions. Early in the series, Satō expressed interest in classmate Aya, but she rejected him after repeated interactions with Kojima. By Volume 2, he confided to friend Rin Suzuki that he and Kojima shared a secret romantic relationship. Their dynamic evolved from accidental encounters to mutual affection, with Satō helping Kojima overcome her insecurities about her intimidating reputation.

Post-graduation, Satō enrolled in university. Bonus chapters reveal Kojima visited him frequently during his studies, culminating in their engagement and cohabitation. He occasionally interacted with others, such as working alongside Wataru Watanabe at a store in Volume 6, where Satō served as Watanabe’s supervisor. His mother, Saki Sato—Kojima’s childhood friend—occasionally interfered in their relationship, including attempts to orchestrate intimate scenarios.