Responses
I think sangwoo just pretended to be mad at Bum when he said he dont feel anything, so he can test how much bum loves him. Hence why he have a huge grin on his face when Bum said, "stay by my side forever!"
Yes, it could be a obsessive love. Probably this is the reason ┗( T﹏T )┛
I think that Sangwoo is a psycho and calculating person. He likes when people suffer, like when he, thinking of choke his mother, he get hard. It's an explanation of why he get mad when Bum said "I don't feel anything".