Nail Fiend

Similar to their partner, the Nail Fiend believes to hold some form of moral principals. Whilst Katana Man respected his grandfather's work as a mobster who only killed "when necessary" and claimed to feel guilt over killing those transformed by the Zombie Devil, his partner criticises the Church for training children to act as soldiers due to valuing their innocence, as well as calling Yoru rude for kicking Fami out of the way of their attack. However, just like Katana Man, they have a major violent streak; most evident when they aggressively struck one of the children they were "protecting" just because they didn't speak politely, likely traumatizing the very children they claimed they were protecting the innocence of. Despite this, their protectiveness of children does seem to be legitimate, as their distaste for the culling of Fire Devil-contracted children is what lead to them betraying Public Safety. Flamboyant and jovial, they also strike poses during combat and involve elaborate flips and slides in their movement, and during casual conversation they rest a hand on their hip. They often refer to other people with terms of endearments - such as calling the Church's children "moppets" or "dears" and Fami "the poor thing" when she was struck by Yoru - and they refer to themselves with unisex language and pronouns in the Japanese version. In addition, they tend to treat dangerous situations with a casual attitude, such as calling the Chainsaw Man Church elder "arrogant" when he morphs into his Devil form, and due to being placed among the ranks of other powerful Devils like Katana Man and Quanxi, they likely have the skill and proficiency to justify this behavior. Nail Fiend seems to find men sexually attractive, as evident by how they laid by Denji's side when he slept. However, they don’t seem to find Denji's rudeness and grossness attractive in the slightest and they quickly lose interest in him.

The Nail Fiend is dressed in the typical office worker and jacket attire of other Public Safety members. Their most notable feature is their face, which is completely split in half. The right half of their face is mostly cracked open and showing only nail-riddled brain matter even though other organs should be present. In particular, there is a prominent crack on their right cheek, possibly as a result of the injury that caused their initial death, or one they sustained prior to it. The left half of their face is covered by a long fringe that reaches down to their nose. The hair on the back of their head is medium-length and flares outward. Their form is rather androgynous; their pants are worn high up their waist similar to female members of Public Safety such as Himeno and Makima, but their torso - especially their chest and shoulders - is far more masculine in shape. They are also drawn with a predominant Adam's Apple, which is typically associated with men. They are also always shown seen carrying a hammer which they use in combat.

As a Fiend, the Nail Fiend can't make contracts with Devils and their powers are considerably weaker than those of their devil form. However, they still have all the other standard devil abilities.