Peter is essentially a 65-year-old retired legendary assassin who gets magically de-aged back into his prime, teenage body. The Vibe: He runs a quiet bookstore but possesses the inner monologue of an exhausted elderly man who just wants a senior discount and a nap. The Reality: Instead, he is forced to use his peak teenage physical form to brutally systematically dismantle his former employer, Glory Club. The Comedy: He fights with a level of cold, calculating "boomer energy" that leaves the younger generation of killers completely traumatized. While other characters scream out flashy, named anime techniques, Peter just relies on decades of pure, unadulterated "I've been killing people since before your parents met" experience.

Johan is another pivotal ally from Peter's past who acts as the operational brains and heavy reinforcement for Peter’s anti-Glory task force. The Vibe: The slick, ultra-competent logistics guy who ensures the murder-spree stays on schedule and under budget. The Comedy: Johan is an incredibly terrifying combatant in his own right, capable of moving at speeds that make regular bullets look slow. However, because he is paired up with Peter—who is basically the grim reaper of the universe—Johan often gets relegated to the role of a highly dangerous, overqualified assistant. He treats dismantling an elite international assassination syndicate like a moderately stressful Monday at a tech startup, providing flawless tactical support while looking impeccably sharp.

Simon is Peter’s old friend from the original generation of Glory Club Apostles. He is a legendary spiral swordmaster who also got betrayed by the organization, but unlike Peter, he didn’t get a magical teenage skincare routine to fix it. The Vibe: An incredibly cranky, lethal old man who is far too angry to die. The Comedy: Simon takes the phrase "toxic personality" to a literal, biological level—his actual blood is highly acidic. His dynamic with Peter is pure gold because he is stuck looking like a senior citizen while his best friend walks around looking like a K-pop idol. Simon spends a good chunk of his time masquerading as a low-level subordinate to trick people, unleashing absolute sword-slashing devastation, and complaining about his joints while Peter flexes his youthful stamina.

Thaddeus is the 10th Apostle of Glory Club and the self-proclaimed "God of Kowloon," but he doubles as the emotional support puppy of an otherwise incredibly depressing story. The Vibe: He is a bright, positive, wholesome ball of energy with striking red hair who is just happy to be included. The Reality: He is an absolute combat mutant who can move his hands so rapidly that he dislocates his opponents' arms before their nervous systems can even process the pain. The Comedy: His entire backstory is built on a hilarious comedy of errors. He dedicated his life to training so he could defeat a mysterious local villain known as the "Demon of Kowloon"—only for Peter to casually drop the bomb that the "Demon" was actually the original Thaddeus, who happens to be Lebbaeus's biological father.

He is a Walking Bottle of AcidMost assassins use guns, wires, or fancy swords. Kageo? He uses his own literal toxic sludge blood. Thanks to some horrific childhood clan experiments from the Dokuhyouryuu syndicate, his blood acts like industrial-strength alkaline detergent mixed with battery acid. If you punch him and he bleeds on you, your flesh melts off. He is the only guy in the webtoon who treats getting stabbed as an offensive power-up. The Ultimate One-Woman SimpKageo’s entire personality can be summed up by his absolute, unwavering devotion to Yuika, the leader of the Kitouryuu clan. He was actually handpicked to be a top-tier Apostle by the big villain Raphael, but he literally said, "No thanks, give the title to my girl instead," just so he could happily play the role of her bodyguard and shadow servant. His dynamic with Yuika was a chaotic cocktail of loyalty, tragic romance, and borderline trauma-bonding. But Yuika is now dead. The Team Switcher Driven by SpiteFor the longest time, Kageo is a brooding antagonist trying to kill our main character, Peter. But the second he finds out that their boss, Raphael, was actually the one who orchestrated the destruction of Yuika’s family, Kageo completely ditches the corporate evil lifestyle. He joins Peter's gang purely fueled by "I am going to tear this whole organization down" spite energy.The "Weakest" God Among MonstersIn the fandom, people love to debate if Kageo is technically the "weakest" member of Peter's current inner circle. But let’s be real—"weakest" in Killer Peter still means he moves at supersonic speeds, slices through B-rank killers like butter, and blocks explosions. He is an introverted, quiet guy who just wants peace, but if you cross his path, you will end up as a puddle of goo on the floor.