Like we only have description so far as proof. There isn't any scene to show that. Even on the first ch where they meet, ML doesn't show any behaviour a lover of underground boss should be like being all over the old man, he just lounging around like he's the boss. Even that old man glance at him for confirmation after hearing MC answer. Pretty sure ML is the actual boss.
Bro that kingdom where he lives sucks so bad!! The king sucks the nobles sucks all of them just fucking corrupt and greedy. Hope ML will whisk MC away to his kingdom in the end. After revenge ofc because wow that kingdom (the king and nobles) deserve it
Tbh that kingdom (the horrible one) sounds like my country lmao