A 25-year-old man named Gaku was a killer. A monster-level talent capable of killing 40 people from the Kanto Branch in just 2 minutes. Recently, he disguised himself as unemployed and moved into a nearby semi-basement apartment without permission. The reason was simple. While living as a member of Slur's group wasn't bad, he had become curious about living alone.

That day, as usual, he was on his way back after cleaning up some targets. He stopped by a convenience store because he was thirsty, and there was a stunningly beautiful part-timer there.