Life is at rock bottom, but assassination is supreme. That is the stark reality of Ryo Nojima, a hitman operating in modern-day Hiroshima. Nojima possesses exceptional lethal skills, yet he lives in grinding poverty. With only 333 yen to his name and the utilities cut off in his rundown apartment, his existence is defined by constant hunger and the next contract. Despite earning millions of yen per job, his disastrous financial sense—wasting money on a woman named Aya and on gambling—keeps him perpetually broke.

Nojima belongs to the ASSASSIN CLUB, an organization that takes contracts through the dark web. The club is small and tight-knit. Uehara is the older, foul-mouthed but reliable handler who negotiates with clients and passes assignments to Nojima. Inui is the weapons specialist who crafts unique assassination tools, including gallium bullets that melt upon firing and leave no ballistic evidence. Nojima does not share deep personal bonds with them, but he trusts them completely and will drop everything to rescue a friend in danger. The club sees itself as nothing more than a bullet fired by the client, carrying out the mission with unwavering fidelity.

Nojima targets those who operate in the shadows beyond the reach of the law. Early on, he eliminates a loan shark who kills a business owner for the trivial offense of late payment. Later, a cunning yakuza named Koda, who abuses his underlings and seeks to control even the assassins, becomes the focus of a full-scale confrontation. Nojima successfully eliminates Koda and his gang.

The most dangerous threat emerges in the form of a sinister cult called Adult Daycare Suiren. This organization preys on the desperate, luring them in with sweet talk and then forcing them into "infantile regression" in harsh conditions to exert total control. For anyone inconvenient, they use a hidden weapon called the Heart Attack Gun. It is revealed that this cult murdered Inui's foster sister, Sayaka, and desecrated her body. Inui harbors a burning desire for revenge and is determined to destroy the cult. When Inui is captured by Suiren, Nojima infiltrates the cult's facility to rescue him, putting himself directly in harm's way for the sake of his comrade.

Nojima is a man of contradictions. On the job, he is cold, precise, and utterly lethal. He is highly sensitive to hostility and can sense danger before it strikes. He has a peculiar habit of wearing a strange headpiece during hits, which always draws puzzled looks from his targets. Off the job, he is evasive and hard to pin down, but his loyalty to his friends is absolute. Uehara speculates that Nojima's reckless spending is a way to release the stress of killing. Nojima, sometimes using the alias Shima Nojo, lives a life of stark extremes: professional perfection and personal ruin, absolute poverty and fierce camaraderie.