"Hiyokoi" centers on Hiyori Nishiyama, a shy and petite high school girl who returns to school after a long absence due to a traumatic accident. Her introverted nature makes it difficult for her to interact with her classmates, and she struggles to adapt to the social dynamics of high school life. Hiyori’s small stature and timid demeanor often lead to misunderstandings, but she gradually begins to open up with the help of her classmates, particularly Yuushin Hirose, a tall and outgoing boy who sits next to her.

Yuushin takes an interest in Hiyori and becomes a source of support, encouraging her to step out of her comfort zone. Despite his friendly and confident exterior, Yuushin harbors his own insecurities, which are subtly revealed as the story progresses. The relationship between Hiyori and Yuushin develops slowly, marked by moments of awkwardness and genuine connection, as they navigate their feelings for each other and the challenges of adolescence.

The narrative explores themes of self-confidence, personal growth, and the importance of human connection. Hiyori’s journey is one of overcoming her fears and learning to trust others, while Yuushin’s role as a supportive friend highlights the impact of kindness and understanding. The series also features a cast of secondary characters, including Hiyori’s classmates and friends, who contribute to the lighthearted and heartwarming tone of the story. Through its focus on everyday interactions and emotional moments, "Hiyokoi" captures the nuances of teenage life and the gradual process of building meaningful relationships.