Until I Came to Be Called "Black Steel King" For Slaying a Bunch of Metal Slimes

Many dungeons suddenly appeared all around the world. It was the era in which both civilians and the army were exploring the dungeon as "Seekers," and brought back the mysterious items with them. One day, Yuuma Mitaka, a 2nd year high school student whose life had nothing to do with dungeons, found a hole in the corner of the garden of his house. When he tried to peek into the hole, he found a metal creature trembling non-stop inside. At first, he had no idea about the hole he found, but knew that the trembling metal creature he found was a very rare monster called a metal slime. "Could it be that this hole is actually a dungeon?" was the conclusion that he came to, and thus began the change of his daily life, coming into the dungeon hole and beating the metal slime. (Source: Kakuyomu, translated)