I Got a Cheat Skill in Another World and Became Unrivaled in The Real World, Too

Isekai de Cheat Skill wo Te ni Shita Ore wa, Genjitsu Sekai wo mo Musou Suru: Level Up wa Jinsei wo Kaeta

All his life, Yuuya has been bullied at school and neglected by his parents. After moving into his late grandfather’s home, he discovers a strange door that seems to be calling out to him. Yuuya opens the door, steps inside, and is suddenly transported to a magical world! This new world holds rare treasures and grants him powerful skills, which he takes back to Earth for a new lease on life.

(Source: Crunchyroll)