Isekai Kenou Seizon-ki

After his military service ends, Hanbin Ryu has no real direction in life — and then gets isekai'd. Standard stuff so far, right? Here's where it gets interesting: the system meant to guide him through this new world is completely broken. Glitched out. So instead of breezing through the tutorial like everyone else, Hanbin is stuck in it for over twenty years. Two decades of grinding through a bugged-out beginner zone, alone, with no end in sight. By the time he finally claws his way out, the world has moved on without him. Worse, society now openly hates otherworlders. So he's technically still a low-level newbie on paper, but he's also someone who survived twenty years of nonstop tutorial hell — which means the gap between what people assume about him and what he can actually do is pretty wide. The setup gives the whole thing a survival-focused edge where Hanbin has to navigate both combat and a world that wants nothing to do with him. There's real weight to the prejudice angle too, it's not just window dressing. If you liked the "returning to a changed world" angle of Uncle from Another World or the underdog isekai energy of Headhunted to Another World: From Salaryman to Big Four!, this one scratches a similar itch but leans harder into the action and isolation. Based on a web manga, so there's source material to dig into if it hooks you.