"Ōsu no Bū-chan" centers on the daily life of Bū-chan, a young boy with a distinctive cowlick hairstyle that resembles a bull's horns. The series is a slice-of-life comedy that explores the humorous and often absurd situations Bū-chan finds himself in, largely due to his unique appearance and quirky personality. The narrative is episodic, with each episode presenting self-contained stories that highlight Bū-chan's interactions with his family, friends, and the people in his neighborhood.

Bū-chan lives with his parents and younger sister, Mī-chan, in a modest suburban setting. His father, a salaryman, and his mother, a homemaker, often find themselves bewildered by Bū-chan's antics, which range from harmless mischief to unintentional chaos. Mī-chan, though younger, often displays a more mature and pragmatic attitude, contrasting with Bū-chan's whimsical and sometimes naive nature. The family dynamic is a key element of the series, with humor derived from their reactions to Bū-chan's eccentric behavior.

The supporting cast includes Bū-chan's classmates and teachers, who frequently become entangled in his misadventures. His best friend, Gorō, is a loyal companion who often joins Bū-chan in his escapades, though he occasionally serves as the voice of reason. The school setting provides a backdrop for many of the series' comedic moments, as Bū-chan's unconventional approach to life clashes with the structured environment of the classroom.

The humor in "Ōsu no Bū-chan" is largely situational, relying on the contrast between Bū-chan's childlike innocence and the absurdity of the scenarios he creates. The series does not follow a continuous plot but instead focuses on the comedic potential of everyday life, with each episode offering a new set of challenges and misunderstandings for Bū-chan to navigate. The tone is lighthearted, with an emphasis on family, friendship, and the simple joys of childhood.

Overall, "Ōsu no Bū-chan" is a comedic exploration of the everyday life of a unique and endearing protagonist, whose distinctive appearance and personality drive the series' humor and charm. The episodic structure allows for a variety of comedic scenarios, making it a straightforward and enjoyable watch for fans of slice-of-life and family-oriented anime.