Naozumi Tsuchida, nicknamed "Tsuchi," teaches the first-year Sakura Class at Hanamaru Kindergarten. Freshly graduated, he started teaching immediately and remains the only male teacher there. Initially seeming unreliable due to inexperience, he grows more capable and confident in his role over time.

His past connects him to Sakura, Anzu's mother, from childhood and high school; she still uses his old nickname "Tsuchi," which Anzu adopts too. He harbored a secret high school crush on Sakura, revealed later. Living alone, he receives occasional visits from his younger sister Satsuki. She worries about him, displays a brother complex, and feels jealous when he interacts closely with his colleague Yamamoto.

A self-identified game otaku, especially fond of the Dragon Quest series, he often stays up late playing, leading to frequent tardiness for work. He develops romantic feelings for fellow teacher Nanako Yamamoto but struggles to express them, hindered by her initial obliviousness to romance. This, combined with his habit of glancing at model magazines and occasionally staring at Yamamoto's chest, earns him the nickname "breast man" among colleagues and students.

He overcomes personal insecurities about confessing his feelings to Yamamoto with unexpected help from his kindergarten students, including Anzu—who has an unrequited crush on him. This results in him successfully confessing and starting a relationship with Yamamoto by the series end. While maintaining a caring yet appropriately distant relationship with all students, his dynamic with Anzu stays platonic and professional despite her persistent marriage proposals and her mother's encouragement, which create awkwardness.