Japanese slang for bipolar
. A yandere character usually have a lot of mood swings. They have a nice side and an evil side, kinda like ying and yang, white and black... those kind of stuff. They quickly change from the nice side to the evil side, and repeat again and again. It is more often used in anime
. There is often another character, usually can be stiff as a board easily, who is normally the 'victim' of the yandere character's evil side.