Jinsei Gyakuten Dungeon

Overview

"I know everything about the dungeon, and I'm gonna turn my life around!" A bullied virgin whose life has hit rock bottom. But when it comes to his knowledge of the dungeon, he's number one in the world. His name is Saeki Kenichi, a high school student. At 16, his magic finally awakens! Kenichi becomes the 'Seeker' he's always dreamed of and heads straight for Dungeon Island—a lawless zone of pleasure and violence!! Using the knowledge he's stockpiled, he'll mow down the strongest monsters and 'release his magic'. (Source: Pocket Comics - Translated)

Source: AniList