Ushimaru had short, somewhat spiky hair that was gathered into a large bun at the back. He had a pronounced nose. 39 years ago, he wore a dark colored yukata with a light colored marking and a light colored jittoku haori with dark colored images of bulls (牛,Ushi?).
Ushimaru served as daimyo for an unknown period of time before 20 years ago, with the komakitsune Onimaru serving as his companion. Twenty years ago, Kurozumi Orochi assumed the title of shogun, and after executing the daimyo of KuriKozuki Oden, he gave the remaining four daimyo the chance to submit to him. The daimyo all refused and staged a rebellion against him. The rebellion was quashed by Kaido, resulting in Ushimaru losing his life.
Ushimaru's name may come from Ushiwakamaru (牛若丸,Ushiwakamaru?), the childhood name of Minamoto no Yoshitsune. Minamoto no Yoshitsune had a retainer named Benkei whose childhood name was Oniwakamaru, which is the possible source of Onimaru's name.