murd's Things

Hello everynyan. I can't remember the name of yaoi manhwa, so please i need your help! So there was a guy and he had a sister who was dating an other guy. And this "other guy" was at first all nice and kind. But it turned out he was a cheater and the conman. And he had sexual relationship with the main character (also i remember as they met at the cafe after some time, it was the workplace for the ml).