The Hidden Dungeon Only I Can Enter

Noir is the 3rd son of a poor noble and his job position is taken away by a more powerful noble. He also sadly lacks enough skills to attend the Hero Academy. He tries to find a way to be able to use his skill [Great Sage] better and stumbles across a hidden dungeon.

In order to find a way to earn enough money for the enrollment fee to the Hero Academy, Noir visits the Adventurers' Guild. However, the receptionist at the guild, Lola, doubts his skills, so he has to prove himself. Once she finds out he's telling the truth, she's supposed to offer him a reward, and...

Noir finds out the social ladder at the Hero Academy. A duke's daughter named Maria is the only one who gives him a helping hand. But he finds out that she has a curse that will kill her when she turns 16.

Right before his meeting with Luna, Noir goes to visit Olivia. He asks her if there's a more effective way to gain LP and she tells him about a forbidden skill that will make him very lucky in the most unexpected way.

In order to gain LP and money, Noir and the others enter a harem tournament. In this tournament, contestants show off their harems to be judged by a harsh crowd. Noir gets close with Emma, Lola, and Luna in order to try to impress the judges and win!

Noir successfully cures Maria's curse and receives a mountain of cash and decides to build a shop that sells rare materials, so he goes to the dungeon to gather said materials. He travels further down and meets a lion that apparently speaks human words.