@radioshit if you still don't understand I'll try to give you a quick resume.
So the delivery boy (jaeyoung) was asked from his late manager to come pick up one member (the red head dude) from his late group from the club.
The Rapper called Happy (The one with glasses aka Seungmin) appeared when jaeyoung tried to get into the club with an excuse that someone order pizza. The pizza jaeyoung's boss gave as a thank you.
Seungmin didn't really think much about jaeyoung and goes to inside the club with him. Jaeyoung gives the pizza and walk off to get the red head.
He goes downstairs because the floor he was on to was the second floor (only for VIPs). The random dude that was messing with him was drunk and irritated. He has a syndrome called photosensitivity which is caused by flashing lights that's why he collapsed when the helmet fell off.
