This thing disarms your taste in about nine minutes and then dares you to keep watching, and you do. Yuuya walks through his dead grandfather's door, punches a bear the size of a truck, comes back to Earth with abs and no glasses, and the show treats that as a complete character arc, because it is one. There's zero shame in it: Night the wolf pup as an accessory, Lexia and Luna competing for a boy who blushes at eye contact, Kaori and Yui and Ayano stacking up like DLC, the sports festival where he casually humiliates the kids who used to shove him. The writing is garbage and the worldbuilding is held together with tape, and the jokes still land because the anime knows exactly what it is and commits harder than shows with ten times the budget. It's the isekai equivalent of gas station fried chicken at 2am. You'll defend it to nobody and finish all 13 anyway.

Yuuya Tenjou's life has been nothing but rejection. His classmates bully him, and his parents neglect him. After his grandfather, the one person who cared for him, passes away, Yuuya moves into the old man's home and discovers a hidden door in the bathroom. Stepping through takes him to an abandoned house in a magical world full of monsters, where he suddenly gains game-style stats and skills. The house once belonged to a sage, leaving behind remarkable weapons, gear and crops with unusual effects. Best of all, the door works both ways, so Yuuya can carry what he gains back to Earth and begin to change his life.