@ismaelh
Perhaps, but I believe he chose to do this since he knew he couldn’t take on Jinwoo himself, so he tried to get his boss involved. His boss, Thomas, did warn him and would be mad, and maybe beat him up, but he knew would never kill him since Thomas is quite biased towards his “assets”.
The only odd thing I find here is that Dong Su or whatever his name is wasn’t particularly close to his brother, so why is he so hell bent on taking revenge? In fact, I recall they were at each other’s throats.
iirc in the novel, it’s more of an issue of pride rather than sibling obligation or ties, but that was never really explored in the manwah, and iirc it was only shown that the dead sibling was mad jealous over his brother’s success and the reason for their fight.