If I was bum I will be really scared and careful all the time,, I mean I become really scared when reading this manga and nothing scares me usually how come this is ordinary!!
he doesn't get scared because he loves this, he likes Sangwoo and he is not conscious anymore. He can't think that maybe Sangwoo is being sweet to fuck him up later, to do something really bad later.
Bum has been abused his entire life mentally and physically, if someone shows him a tiny bit of kindness, he will cling to them regardless of how they treat him! He need some therapy!
This ain't ordinary liiiiife