In the original book series, Tapu acts as an older brother figure to Mei within their goat herd on Sawasawa Mountain. He is characterized as an overweight goat who provides protective guidance and support to Mei, offering stability as she faces challenges from an unconventional friendship.

The 2012 television adaptation *Arashi no Yoru ni: Himitsu no Tomodachi* significantly redesigns Tapu, depicting him as more fit physically. This adaptation introduces an openly acknowledged romantic interest in Mei, portraying it as a recurring unrequited crush. The series incorporates comedic and dramatic tension through Tapu's repeated attempts to confess his feelings to Mei, which are consistently thwarted by external events or circumstances, leaving his romantic subplot unresolved.

This unfulfilled romantic arc shapes Tapu's narrative presence in the television series, contrasting with his original book portrayal where romance is absent. While his core function as a supportive figure within Mei's social circle remains consistent, the anime adaptation expands his personal motivations through this persistent, unresolved affection. Tapu does not appear in the 2005 animated film adaptation, the kabuki stage production, or any spin-off media; his significant development is limited to the original books and the television series.