I really got the feeling Bumi said that about the shirts and his uncle on purpose. The way he smiled when he saw Sangwoos hardened face and him quickening his pace, it's the way Bum smiles when Sangwoo is kind to him or what I'm beginning to think, when Sangwoo shows weakness for him. Also the whole lingerie thing, he smiled that same weird blushy smile. Sangwoo may be grooming Bumi to be a better killer or to kill his uncle but Bumi is grooming or rather manipulating Sangwoo just as much. I don't know what his intentions are or if he even knows what he is doing but I'm expecting shit to come down again next two episodes.
Sooo... He got a make-over?