Using the limited information I found, let me paint the picture: A bro-dude and his bro-buddies are out for a night of bro-fun in Korea (exact location uncertain). He’s probably had a few drinks and is wandering down the party street where he encounters an unusual busker: an ex-boxer who is letting people punch him repeatedly for money.
Because our bro-dude is clearly all man, and probably being goaded on by his bros, he decides to partake in this thoughtful, moving cultural experience. In order to make this activity resoundingly idiotic rather than just disappointing, he instructs the ex-boxer to punch back, even though he’s a little tipsy, obviously has no training and is not wearing headgear. The ex-boxer, who is amazingly the least idiotic person in this idiot cabaret, compromises and says he’ll only punch with his left hand.
Good clean fun turns to cocky overconfidence, which turns into… Well, you’ll see.