Five years ago, Ryō killed his Yakuza partner Niko—right after watching Niko murder the woman he loved.

Now living as Hiroshi Ichihara, a quiet college student, he’s buried his past and all the blood on his hands. A second chance. A normal life.

Until a first date shatters everything.

Forced to reveal himself, Ryō discovers the impossible: Niko is alive. Worse, he's united the Yakuza clans and engineered a CRISPR virus that could end civilization. Only one person can stop him—the assassin Ryō swore he'd never become again.

But there's a price. Every kill awakens the darkness inside him, the bloodlust that made him Tokyo's most feared killer. The more he fights, the more his humanity slips away.

With Ayako Yanagi—a brilliant doctor caught in the crossfire—as his only ally, Ryō must return to Tokyo’s underworld to infiltrate Niko’s genetically enhanced army and stop the virus before it’s released. But defeating his former brother-in-arms may cost him the one thing he’s fought to keep: his soul.

Can he save the world without becoming the monster he’s always feared?