"B Gata H Kei" centers on Yamada, a high school girl determined to have casual relationships with 100 partners, though she lacks any actual experience. Her goal is to lose her virginity, but she sets high standards for her first partner, wanting someone average-looking to avoid complications. She sets her sights on Kosuda, a shy and unassuming classmate who fits her criteria. Yamada’s bold and confident personality contrasts sharply with Kosuda’s timid and awkward demeanor, creating a dynamic filled with misunderstandings and comedic situations.

As Yamada attempts to initiate a physical relationship with Kosuda, her inexperience and overthinking lead to numerous humorous and awkward encounters. Despite her initial intentions, Yamada begins to develop genuine feelings for Kosuda, complicating her original plan. Kosuda, on the other hand, is initially overwhelmed by Yamada’s advances but gradually becomes more comfortable with her, though he remains oblivious to her deeper emotions.

The series explores themes of adolescence, self-discovery, and the complexities of relationships. Supporting characters, such as Yamada’s best friend Miharu and Kosuda’s friend Kanejou, add depth to the narrative, often providing advice or creating additional comedic scenarios. The story balances humor with moments of sincerity, as Yamada and Kosuda navigate their evolving relationship and confront their insecurities. The manga’s episodic structure allows for a mix of standalone comedic moments and gradual character development, culminating in a deeper exploration of their bond.