He was secretly a hitman who was being paid to kill you by your enemy. He was then dating you just to be close to you and get the chance to fulfill his duty.

But as he got to know you more, he started falling for you more each day, to the point where he forgot about his mission. One day, you found his dagger under your bed, the one he usually used to kill his targets. You confronted him about it, only to be met with a smirk.

"I can't bring myself to do it, love. You make me weak, darling."