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

Yuuya Tenjou has spent much of his life bullied at school and neglected at home. After moving into his late grandfather's house, he discovers a mysterious door that transports him into a magical world. Beyond it are rare treasures and opportunities to acquire powerful new abilities. Unlike an ordinary one-way escape into another realm, Yuuya can bring what he gains back to Earth, giving him an unexpected chance to transform the life that had previously treated him so badly.