Taisho-kun, who also goes by Boss, is a field hamster and the self-appointed leader of the Ham-Ham gang. He presents a gruff, short-tempered exterior but proves to be dependable, courageous, and kind, occasionally revealing a shy side, especially around some female hamsters. He owns and lives in the Ham-Ham Clubhouse, the central gathering spot for the group. He stands 12cm tall, making him the tallest of the Ham-Hams, with cream and dark brown fur and a visible belly button. He is rarely seen without his yellow helmet adorned with a green stripe and a red crescent, and he carries a shovel. His Japanese name, Taisho, means "boss" or "leader," a title that suits his desired role. His background as a field hamster grants him greater independence and a natural familiarity with the outdoors, along with a unique "field hamster sense" that warns him of weather changes. He is highly susceptible to seasickness and struggles with ocean settings. His personality blends bravado with deep loyalty. He often acts as if he knows everything, though these boasts regularly backfire. Despite this, he is deeply caring and would sacrifice his own helmet and shovel to help another Ham-Ham. His favorite expressions are "Daji~e!" and "Dabba-to!". He harbors a long-standing, unreciprocated crush on Bijou, a hamster with blue ribbons who once lived in France. Her interest in Hamtaro fuels his jealousy, though they remain friends. Over time, his feelings for Bijou fade as he develops crushes on other hamsters, including Harmony, Oshare, and Gelato. His affection for Gelato is returned, marking his first mutual romance. He shares a strong friendship with Hamtaro, whom he regards as an older, wiser figure—a bond he initially underestimated. He also maintains a quiet, meaningful connection with Snoozer, a perpetually sleeping hamster who offers unexpected wisdom. Another key relationship is with Sabu, an older field hamster he admires as an older brother and often turns to for guidance in matters of confidence and romance. A significant story arc involves him leaving the clubhouse to embark on a long journey. During his absence, the clubhouse is hidden and the group finds a new meeting place. He returns adopting a "Hero-Ham" persona, a secret identity he uses to aid others anonymously. He continues this role periodically even after his identity is revealed to most. He was discovered by Boss in the hideaway that became the clubhouse, and his origins remain unknown. He is one of the only hamsters shown to possess a belly button.