Honestly Bum should have kept it, but had a mini couple argument about how good his memory is and how Sangwoo is the one who forgets everything. Or Sangwoo could be like "I said my memory was good? It must have been a slip up because how nervous I was." Bum erasing because of what Sangwoo said is just so suspicious. （￣へ￣）
So they just not working huh? ╮(￣▽￣)╭