What is define yandere?

Yandere is a term used in Japanese manga and anime culture to describe a character who is initially sweet and kind but becomes obsessed with their love interest to the point of becoming violent and dangerous. Yandere characters typically display a range of unsettling behaviors, such as stalking, threatening, and even harming others who they perceive as posing a threat to their relationship. The term "yandere" is derived from the Japanese words "yanderu," which means to mentally or emotionally break down, and "dere," which means love-struck or infatuated. The yandere archetype has become increasingly popular in manga, anime, and video games over the years, and is known for its intense and often disturbing portrayal of love and obsession.