An odd, yellow, shape-changing creature, his name (roughly, "sonic ball") is fairly descriptive. He is usually depicted as a round, yellow sphere with a face, variably with wings or arms, deep voice, and a loud temperament. He has the ability to produce legs at will. Often, when getting emotional, he will transform into an extremely muscular full human body, with himself as a round yellow head on top. In spite of being such a bizarre creature, he is for some reason the leader of Shinobu's ninja clan. Nobody really knows what kind of being he is, but it is said he has a sister, and Shinobu refers to him as a hawk, even when Kaede shows her a picture of one. Onsokumaru is perverted, lecherous, messy, loud, a cheat, and greedy, and he even poses as a ninja master for Shinobu, who can't tell. He imagines softcore-pornographic fantasies about Shinobu and Kaede, either for his own personal pleasure or to enthrall or persuade the male ninja into helping him. It is also mentioned that he has an incestial crush on his sister. On the other hand, he is often friendly, and has a silly playful side.