The premise is that the protagonist is a loser, he's such a loser that he is borrowing money to his GF on a cafe for gambling, then MC was offered a contract by a woman and that contract is that he must go to another world and save it. I remember when he finished his training in the other he can go back to the real world then he went back to the cafe to pay his GF but she doesn't want to see him anymore.

After a while MC formed a party with the companion from his training days and they conquered a castle and a secret dungeon.

That's all I remember from that series.

The Second Coming of Gluttony

~4400 manga completed
~1700 ongoing...