Gaku, a 25-year-old man, was a killer by profession. A monster-level talent capable of killing 40 Kanto Branch members in just two minutes. Recently, he disguised himself as unemployed and moved into a nearby semi-basement apartment without permission. The reason was simple. Living as part of Slur's group wasn't bad, but 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 he saw an incredibly beautiful part-timer.