Killing Stalking

Yoon Bum is a young, mentally ill man with a difficult past. After becoming infatuated with Oh Sang Woo, a peer from his time in the military who saved him from a rape attempt, he decides to enter Sang Woo's home while he is out of his house. Yoon Bum finds a tied up, bruised woman in Sang Woo's basement and before he is able to free her, he is discovered by Sang Woo, who is revealed to be a serial killer. Sang Woo then breaks Bum's ankles and despite Yoon Bum's previous love for him, Sang Woo puts Bum into a highly abusive and manipulative relationship until the very end.
(Source: Wikipedia)
~~ Adapted from the webtoon "Killing Stalking" (킬링 스토킹) by Koogi (쿠기).