Sankichi Okuda, universally known as Moo-chan, forms one-third of a central sixth-grade boy trio. His notoriously slow pace defines him, consistently making him late for school and coloring his entire unhurried approach to daily life.

This deliberate nature leads him to interpret situations literally, sometimes causing misunderstandings. He once misinterpreted a classmate's desperate toilet-paper plea signaling a burglary simply because he couldn't read the word, showcasing his straightforward problem-solving and occasional comprehension gaps during tense moments.

He actively participates in typical childhood escapades with his friends, joining ghost-doll pranks aimed at girls and explorations of local historical sites like castle ruins. While often humorous, these adventures sometimes lead him into encounters with more serious subjects, such as uncovering wartime bomb shelters.

Within the trio, Moo-chan's easygoing nature provides a distinct counterpoint to his friends' energetic traits. He remains a steady, reliable presence in their escapades, though often perplexed, fueling both comedy and light drama through his unfazed reactions and interactions.