San is known as Princess Mononoke, the 17-year-old girl, princess of spirits and beasts. When San was a baby, her parents, along with some other travelers, were attacked by the wolf goddess Moro. Her parents threw San to Moro as a sacrifice to save their own lives, thus escaping while Moro was preoccupied with San.

However, San was spared; Moro did not eat her, instead raising San as her own daughter. San treats Moro as her mother and her two natural pups as brothers. San rejects her own humanity, thinking of herself as a wolf. Possibly because of her past, San hates humans with a great ferocity, even more so than Moro. She wears a coat made of wolf hide, and carries a dagger made from the tooth of a wolf.

San cares very much for the forest she lives in and the animals she lives with. San is very agile, able to dodge arrows, darts, and even ishibiya shots. She, like the Mountain Spirits, wants to destroy the humans so that they will stop taking away all their land. She personally wants to kill Eboshi, the leader of Irontown.