Ji Qingchen, the craziest gangster on the streets of Donghua City, idles around all day but calls himself a gangster. In a desperate situation when he was being chased by his enemies, he accidentally activated the "Ultimate BOSS Sign-in System". This cheat allows him to check in at a specific location every day, and he can get heaven-defying rewards - from the "Devil God's Crazy Bone" power to the "Dark Emperor Technique", from hiding his identity to establishing underground forces.
As the check-in location shifted from the streets to urban restricted areas, Ji Qingchen discovered that the world was far from simple as it appeared. A group of supernatural beings who call themselves "Skywalkers" are secretly eliminating all potentially powerful beings. They possess various evil powers and regard ordinary people as ants. The Skywalker organization became aware of Ji Qingchen's rise and listed him as the number one target for elimination.
Facing Skywalker's encirclement and suppression, Ji Qingchen escaped from death time and time again by relying on the superpowers obtained by signing in. He is no longer satisfied with being a street gangster, but wants to become the true dark master of the city. From the hunted ant to the existence that makes Skywalker frightened, Ji Qingchen signed all the way and became a devil. When the final battle came and everyone thought he would be wiped out by the Skywalker Alliance, Ji Qingchen stood on the ruins and showed a wild smile: "I'm sorry, the place where I signed in today is your home base."
