On his way home from his office, the main protagonist drove and ran over a big dog. At that moment, he heard the sudden sound of a voice inside his head. The monster has been subjugated, gaining experience points. Eh? Before anyone knew, the world has changed. Monsters appear, this is a game-like world where levels, skills, and status exist. This is an adventure where the modern world becomes fantasy and where the main protagonist has to strive hard for his survival.