Five years have passed since dungeons suddenly appeared on Earth. Yashiro Yoiichi, a highly skilled explorer who challenged dungeon raids from the very beginning, was once seen as a rising star. But during one expedition, he was attacked by an irregular monster known as a "Trial Beast," losing the sight in one eye. Branded a failure and cast aside as a washed-up explorer, Yoiichi refuses to give up. Armed with a unique power unlike anything else, he rises from the very bottom to strike back.