Isekai De Cheat Skill Wo Te Ni Shita Ore Wa, Genjitsu Sekai Wo Mo Musou Suru ~Level Up Wa Jinsei Wo Kaeta~

Story:

Tenjou Yuuya is a cowardly boy who has been brutally bullied by his classmates since childhood. When he found his grandfather's old room where he stored various items he collected while traveling the world, he found a door to another world…