Usawaka-Maru 兎若丸
A youkai of the Heian Period. He was the partner-in-crime of Shuri/Benkei back in his villainous days. He resents Princess Shizu for leading Shuri away from the path of villainy. He is considered a great androgynous beauty (bishounen). He wields powerful magic but is also clumsy and prone to mistakes.
Usawaka's gender is ambiguous at first, but later chapters make it clear that he is a boy.