I'm going to be real with you guys, it's not a good Manga.
I don't read LNs, so maybe the story is better there, but this Manga is not worth the read.
An OP MC visits a Magic School. Everyone thinks little of him, until he shows that he's at least 40 times more powerful than the next student in line. How does he show?
Well, they are some kind of Monster-Races and their task is to create their first dungeon. Everyone does like 5 floors, 10 is considered extraordinary.
Well, our MC does 400 just like that.
Anyway, it's not really important because all he places in there is a bed for him to sleep in. What happens? He wakes up with a cute Vampire girl next to him. He enslaved her by accident. And then he goes and enslaves another girl by accident.
And all the people around start to like him. Yeah.
He's also from that super mysterious Village so he thinks he's average but he is actually super powerful... as the Manga develops so far this feels like written by a elementary Schooler who explains his OC Superhero.
Thing is... the "Guy who thinks he's mediocre but is actually from a super powerfull region" Plot is also done by "Tatoeba Last Dungeon Mae no Mura no Shounen ga Joban no Machi de Kurasu Youna Monogatari" just that it's way funnier.
While This story is played straight as hell, Last Dungeon is at least exaggerated and funny.
I rate this 1/10 because I think "pathetic" is what fits this Manga best. Stil gonna read it, if it ever updates - might get better.