Although it Is a Company Slave, I Reach the Strongest by Race Evolotion

Akito Fujimura is a company slave that he and others recognize as a company slave. When he returned home exhausted from not sleeping for days on end, he found something that looked like a dungeon growing in his garden. Suspecting that it is a project for a TV show, he goes inside and encounters a goblin. Still, he remained unfazed and fought, but he defeated him normally...!? The world changed from that day onwards. Monsters appeared from the suddenly created dungeon and started roaming the city, transforming the world into something like a game. In such a situation, Akito achieves racial evolution by simply training in the dungeon, and climbs the stairs to become the strongest Source: MU