Princess Mononoke

In medieval Japan's Muromachi period, young Emishi prince Ashitaka kills a rampaging demon boar to protect his village but receives a spreading curse on his arm in the process. The boar was once the god Nago, corrupted and driven mad by an iron bullet lodged in its body. A village elder tells Ashitaka the curse will kill him; he must journey west to find the source and seek a cure. During his travels he discovers the curse grants him superhuman strength. A wandering monk named Jigo points him toward the Forest Spirit, a deer-like deity living in the western mountains that transforms into a towering giant at nightfall. Following luminous kodama sprites, Ashitaka glimpses the Forest Spirit and also witnesses an ongoing conflict: the wolf goddess Moro and her human-raised daughter San (called Princess Mononoke) are at war with Lady Eboshi's Irontown, a fortified iron-smelting settlement built from cleared forest land. Arriving at Irontown, Ashitaka learns that Lady Eboshi deliberately shot Nago with an iron bullet, triggering his transformation into the demon that cursed Ashitaka. Eboshi plans to kill the Forest Spirit entirely so her town can expand unchecked. Despite her destructive ambitions, she treats the town's residents — former prostitutes and people with leprosy — with genuine compassion, complicating Ashitaka's moral view of her. Jigo, revealed as a mercenary, is conspiring with Eboshi to obtain the Forest Spirit's severed head, which is rumored to grant immortality and has been promised as a prize by an unnamed emperor. When San infiltrates Irontown to assassinate Eboshi, Ashitaka steps between the two to prevent further bloodshed. He is shot, but his curse-enhanced strength allows him to carry both San and an unconscious Irontown worker to safety. The Forest Spirit heals Ashitaka's bullet wound but does not lift the curse. Meanwhile, a blind ancient boar god named Okkoto leads his clan in a desperate, suicidal charge against Irontown's rifles; they are slaughtered. San accompanies the mortally wounded Okkoto as he retreats, but Eboshi and Jigo secretly follow them, using the bodies of fallen boars as camouflage to track Okkoto toward the Forest Spirit's sacred pool. Okkoto's agony and grief cause him to transform into a writhing demon of hatred, threatening to consume San along with everything around him. Moro sacrifices herself to drive through Okkoto and free San. The Forest Spirit grants both Okkoto and the dying Moro a merciful death. Eboshi then beheads the Forest Spirit as it passes in its Nightwalker (giant) form at dawn. The headless body becomes a catastrophic force, spilling a black death-fluid that consumes the forest and the surrounding land. Moro's severed head, animated by final vengeance, bites off Eboshi's arm before going still. Ashitaka and San race after Jigo, who is fleeing with the Forest Spirit's head in a box. Ashitaka evacuates Irontown's residents from the spreading destruction while San pursues Jigo. Together they wrest the head away and return it to the Nightwalker body just as the sun rises. The reunited Forest Spirit dissolves and dies, releasing a burst of life energy that rapidly regenerates the devastated landscape with new vegetation. Ashitaka's curse disappears completely. In the aftermath, a humbled Eboshi resolves to rebuild Irontown in a better way, and the surviving townspeople begin anew. Ashitaka tells San he will live in the forest to help her; San, though she loves him, tells him she can never forgive humanity. They agree to see each other, living separately but connected across the boundary between the human and natural worlds.

Sources: Wikipedia