From what I remember the MC reincarnates (it could also just be the born son of the lord of this city) as the son of a lord of a large dungeon city, and like as he grows up wants to monopolize the dungeon and trains himself and the knights to deal with the dungeon as well as has a small party of elites he raids the stronger dungeons with. I am pretty sure this is a manga and if I remember right his father was a Marquis/Margrave or a Count.