"Sex Education 120%" is a manga series that explores themes of adolescence, relationships, and sexual education through the lens of a high school setting. The narrative centers on a group of students who form a unique club dedicated to learning about and discussing topics related to sex and relationships, often addressing misconceptions and societal taboos. The protagonist, a reserved and curious student, joins the club after encountering various personal struggles and misunderstandings about intimacy. Alongside the protagonist, the club members include a diverse cast of characters, each bringing their own perspectives, experiences, and challenges to the group dynamic.

The story progresses as the club tackles a range of subjects, from basic anatomy and consent to more complex issues like gender identity, sexual orientation, and emotional vulnerability. The interactions between the characters are marked by moments of humor, awkwardness, and heartfelt sincerity, reflecting the realities of navigating such topics during adolescence. The series balances its educational focus with character-driven storytelling, delving into the personal lives and growth of the club members as they confront their insecurities and build stronger connections with one another.

Throughout the manga, the club's activities often intersect with broader school life, leading to conflicts, misunderstandings, and occasional breakthroughs with their peers and teachers. The narrative emphasizes the importance of open communication, mutual respect, and self-discovery, presenting these themes in a way that is both informative and relatable. By addressing sensitive topics with a blend of sensitivity and realism, "Sex Education 120%" provides a thoughtful exploration of the challenges and triumphs associated with growing up and understanding oneself and others.