The name Tarou Sakamoto once instilled fear in every villain. No other professional hitman matched his prowess, and fellow assassins revered him. However, Sakamoto fell in love. In five short years, he married, became a father, put on some weight, and traded his weapons for an apron as he became the owner of a humble convenience store. Although Sakamoto is decidedly retired, he finds his old life of crime hard to shake off. His former partner, Shin Asakura, reappears and resolves to stay with Sakamoto's family under their strict no-kill rule. To make matters worse, a large bounty is placed on Sakamoto's head. Numerous assassins now pursue him—but they are in for a surprise. Sakamoto has not lost his edge, and no matter what tricks his enemies pull, he will fight off every last one to protect his dear family.

The entire universe is divided into the inner universe and the outer universe. The two universes are enemies of each other. The outer universe is ruled by demons, and the inner universe is divided into The Realm of gods, the Eternal Realm, and the Mortal Realm. In the universe, there are countless mortal worlds like the Tianfa Continent, and they are collectively referred to as the Jiutian Xin Region. In the field of Jiutian Xin, nine immortal emperors commanded all star fields in nine layers. Above the nine heavens is the realm of purification of immortal gods.

In a fantasy world where "jobs" are god-given from birth, heroes are born, not made—and Ein's job of "Appraiser" has put him about as far from the "hero" pedestal as possible. Used, abused, and eventually abandoned by his fellow adventurers, Ein decides it just isn't worth going on. Lucky for Ein, though, the end may just be the beginning, as well as a new lease on life. Turns out, his "worthless" job may just be the key to becoming a hero after all.

One night at a rock concert, a mysterious man dies while leaving a floppy disc with a member of the Rutz Detective Agency. Soon they realize the disk contains information about a deadly new weapon under development. The heroes become involved in a game of political subterfuge and military espionage, hot on the trail of the killer!