Manabu Hara teaches music at the all-boys Touichikou High School. As a gay man, he adheres to a strict policy against relationships with current students, despite harboring romantic feelings for pupil Rihito Sajō. This sparks friction with Hikaru Kusakabe, Sajō’s protective boyfriend, who dubs Hara "Sekuhara" and physically confronts him when Hara oversteps boundaries during Sajō’s vulnerable moment. Paradoxically, Hara later mentors Kusakabe on relationships and sexuality.

Hara’s history involves unreciprocated affections, beginning with an intense attachment to his former teacher Satoshi Arisaka. Their shared kiss during Hara’s student days prompted Arisaka’s departure from the school. Years later, when Arisaka returns as a substitute teacher, Hara aids in reconciling Arisaka with his younger partner, Hibiki Sano.

After Sajō graduates, Hara meets current student Aoto "Sora" Sorano in Shinjuku’s gay district. Hara initially rejects Sorano due to his student status, but Sorano engineers a meeting between Hara and Sajō, granting Hara emotional closure. Sorano later challenges Hara’s self-sacrificing nature, leading to a kiss though both agree against an immediate relationship.

Once Sorano graduates and becomes a fashion model, he and Hara reunite romantically. Hara attends Kusakabe and Sajō’s wedding, signaling reconciliation. Students nickname him "Harasensei" or "Sekuhara," blending his name and reputation. Standing 185 cm tall, Hara navigates life as a lonely figure marked by romantic setbacks before stabilizing his connection with Sorano.