Not all rumors are true.. Sometimes bad things happen to good people

[COMPLETED] [Yandere Ex X Reader] Y/N's Ex could not leave her alone, he wanted her back and he would do anything to have her back, no matter what it was. Nobody could have Y/N nobody but him.

(F/n) leads a happy life with her boyfriend, Ash. In the harmonious state, what could possibly turned him into a different person?