I'm thinking Sungbae only said that to get Bum to tell the truth. I'm confused how he found out Bum killed Min Jeun or whatever her name is. That could've been a set up too, but I don't know about that.
You are right...they never confessed to anything...the cop was making it all up. The part where he said Bum killed Min Jeun was also just a lucky guess, he was just trying to make it seem like Sangwoo was blaming Boom to pin them against each other and get Bum to think Sangwoo betrayed him.
Remember when his friend was on the phone with him saying the cops think bum is a suspect because of how badly she was talking about him.
I don't remember that :(( I'm gonna need to reread this
I was so frustrated when bum wasn't telling the truth, and how is sangwoo free after he confessed to everything???