Depressing love/ Taehyung

It's about a happy young couple that have been dating for over 2 years, then that all changes when Taehyung (the male) father was suspiciously killed and no one knew how or why his father died, after that death the young boy went into a deep depression, but his depression was not for the right reasons to be depressed he was acting odd and a bit crazy, not common for the boy, so his girlfriend wondered what really is happening in her boyfriends head.