San is a beautiful young woman of average build (around 16–17 years old) who wears ragged clothing and a cape made of wolf's fur and has what appears to be red war paint on her face. Her hair color is brown. She is also very agile, fast, fairly strong, and appears to be really good at using daggers and spears. She wears a mask which is her iconic feature. The mask is red with ears and red wavy lines and three yellow holes for a mouth and eyes. She later wears Kaya's Crystal Dagger after Ashitaka gives it to her as thanks for saving him.
San is a young woman raised by the wolves and feels hatred for humans, but eventually comes to care for Ashitaka. San is stubborn and protective, her primary concern being to protect the forest and animals she lives with. San rejects her own humanity, seems to be quite misanthropic, and thinks of herself only as a wolf. Despite this, she eventually falls in love with Ashitaka; however, she decides to live separated from humans as she cannot forgive.
In the film
When San was a baby, the wolf goddess Moro attacked her parents, who were found damaging the forest. San's parents threw her to Moro as a sacrifice to save their own lives. Moro raised San as her own daughter, and in turn, San treats Moro as her mother and Moro's two natural pups as siblings.
San’s primary concern is protecting the forest and the animals she lives with. San rejects her own humanity and even thinks of herself as a wolf. She has attempted to assassinate Lady Eboshi of Irontown many times, as San believes that Eboshi’s death will result in the end of Irontown and human growth into the surrounding, untouched forest. It is only by Ashitaka's affection to her that she slowly comes to acknowledge her human side as well. Then she realized Ashitaka was badly wounded, and saw the ape tribe to get the human. San brought him to the Forest Spirit to heal his wounds from the bullet. The boar tribe arrived and when Lord Okkoto came to Ashitaka, she saw that Okkoto was blind. When the boar tribe leaves, she saw the Forest Spirit drinking water.
San and the wolves came to the camp, and she smells that the scent from the green fire stinks. A wolf brother came with a Crystal Dagger from Ashitaka that he's holding. After the battle, San is going to bring Okkoto to the Forest Spirit, and on their way, she heard a howl of a wolf brother that she realized it was Ashitaka. After Moro saved San, she asked Ashitaka to save her that he loved.
After the battle for the Forest Spirit's head, San tells Ashitaka that he is very dear to her. However, she cannot forgive the human race for what they have done to the forest and will continue to live apart from them. San returns to the forest while Ashitaka remains in Irontown. Before separating, Ashitaka promises that he will always be near and visit her in the forest whenever he can. San reciprocates his declarations and leaves.
- The character of San "Princess Mononoke" proved so popular with the staff at Studio Ghibli they renamed the film from the initial title, "The Legend of Ashitaka" to the eponymous title after her.