The "Rapper" career and the club is a set up bait to catch the "Happy" drug maker/distributor.
The said drug originally circulating in Brazil has made so much people suffer.
ML's organisation has chased them bad guy out and found some hint that they would be operating in South Korea.
And to find them, you gotta lure them.
So they set up 2 baits.
"Famous rapper on the rise"
"A suitable club to increase the effect of the drug".
Ironically, that day they first met (ML love at first sight), MC was the one got caught in the bait (the lights that increase the effect of the drug).
At that time ML have no idea.
But as he love more and want to know what happened to MC to help him...
He start to realised the connections.
I love how gentle he is with him ╥﹏╥ also i feel a little dumb but what's going on with the ml-brazil-drug plotline?