Tatsuo Kusakabe is a university archaeology professor who moves with his daughters, Satsuki and Mei, to the Japanese countryside to be near his wife Yasuko, hospitalized with a long-term illness. He has dark hair, dark eyes, slightly tanned skin, a tall, fairly skinny build, and wears glasses. His typical attire includes shirts, pullovers, a red vest, blue trousers, or a white undershirt.

He demonstrates patient, warm, and encouraging parenting. When Mei reports meeting Totoro, a forest spirit, he validates her experience by suggesting it is indeed a spirit. He similarly engages with their belief in soot sprites, joining them in laughter to help dispel the creatures, prioritizing their emotional support. He reassures Mei when she is distressed about finding Totoro's tree, stating the spirit will appear when ready. While providing practical care, he occasionally becomes absorbed in work, missing meals.

His relationship with his daughters is affectionate and playful; they cling to his arms as he runs, forming a "human jungle gym." He balances academic work at home with family time, ensuring the girls feel secure despite their mother's absence. During hospital visits with Yasuko, he expresses concern that Satsuki shoulders too much responsibility and shares family updates. Discovering an ear of corn left by the girls inscribed "For Mommy" reflects their mutual care.

A novelization reference to him singing a song associated with Hokkaido University suggests a possible connection to Hokkaido, though his background beyond this remains undefined. His character remains stable throughout the narrative, providing familial stability without significant change. He does not appear in spin-offs like *Mei and the Kittenbus*. His role centers on maintaining family cohesion amid uncertainty, bridging everyday life with his daughters' encounters with the natural and spiritual worlds.