Ranma ½ (1989)

S01E59 Ranma and the Evil Within

Happosai uses a mystical incense to divide Ranma into his male and female forms. To Ranma's shock, his female counterpart absorbs all of his darker traits, transforming into a malevolent spirit intent on dominating the male Ranma. This sinister entity seeks to control him, leading to a battle of wills as Ranma must confront the dark side of his own nature.