Komari Otenjo. 108 years old. Demon side. A young girl Demon King with glossy black hair in a bob cut and two small red horns, wearing a gorgeous kimono larger than her own height. She always holds a five-colored handball (temari) and stares blankly with large round eyes. Her personality is extremely gentle and she moves at her own pace; she lacks any sense of crisis to the point of preparing a welcome party when humans attack. She speaks in a slow, childish manner. She dislikes conflict entirely and spends every day eating sweets and napping on the top floor of the castle. Because of her extreme loveliness and innocence, she is doted upon by Mio and Yachiyo.

Tsubaki Tenran. 21 years old. Hero side. A female Hero clad in white robes and a crimson haori, effortlessly wielding a massive odachi as long as she is tall. She is characterized by dignified upturned eyes and a glossy black ponytail. Born as a daughter of a distinguished samurai family. After grueling training, she obtained overwhelming combat power that stands out even among successive Heroes, but at the same time, she developed an extreme sense of justice, believing that "demons are an absolute evil that will destroy the world." She shouts in a stiff, samurai-like tone and interprets all of the opponent's explanations as "despicable traps," crushing them with physical force. She has enough combat power to reach the 8th floor with ease.

Mio. 70 years old. Demon side. A Queen Slime taking the form of a voluptuous woman, translucent and pale light blue. She wears a beautiful kimono but is constantly frightened and trembling all over. Her personality is that of an extreme coward and a crybaby. She hates conflict and runs away screaming when a Hero appears. However, she is one of the Four Heavenly Kings for a reason, possessing a flexible body that completely negates physical attacks and powerful acid that melts any weapon it touches. Having grown up in the peaceful environment of the Demon King's Castle, she has zero will to fight. She is entrusted as the gatekeeper of the 6th floor.

Yachiyo Kumo. 80 years old. Demon side. A Jorogumo (spider yokai) with glossy spider legs growing from her back, wearing a lab coat over her kimono. The third member of the Four Heavenly Kings. She is extremely intellectual and full of curiosity, speaking in a syrupy, polite tone. She habitually uses Mio as a guinea pig for new medicines and traps, making her cry, but she is strangely close to her, rewarding her with special tea sweets after experiments and going on sweets tours together on holidays. She is extremely serious about her work. She is entrusted as the gatekeeper of the 7th floor.

Goga. 98 years old. Demon side. A silver-furred wolf beastman (male) with a massive physique exceeding 2.5 meters. He wears a rugged black jinbaori and hakama loosely, carrying the field sword "Tenroumaru" on his back. He is greatly feared for his sharp gaze and scarred face, but he is actually the most caring and sensible person among the Four Heavenly Kings. He speaks bluntly in a low, gravelly voice. He used to be a hot-blooded brawler, but now his hobby is serving handmade wild boar hot pot to the grunts. He is entrusted as the gatekeeper of the 9th floor.

Botan Saionji. 21 years old. Hero side. A Japanese-style healer with a plump, voluptuous figure and a constant, gentle smile. She wears a luxurious light pink miko outfit slightly disheveled and often grips a giant bone-in meat instead of a shakujo staff. She has a laid-back personality and speaks in a slow, kind tone, but inside she is a pure muscle-head. Born into a family of famous onmyo-doctors, she awakened to a severe love for meat and fried food as a reaction to a strict vegetarian diet. She invades the Demon King's Castle as the healer for Tsubaki and Nadeshiko's party, but her true goal is to eat the "Legendary Fried Chicken Set" said to be in the castle's cafeteria.

Nadeshiko Shinra. 21 years old. Hero side. A lovely girl with glossy black hair in twin tails, wearing light armor modified from a cherry-blossom colored kimono... or so it seems, but he is actually a cross-dressing boy. He is aware of his own cuteness, but usually acts very timidly, worried that Tsubaki and Botan will find out he's a boy. However, when it comes to battle, he is a natural attacker who effortlessly swings a massive odachi larger than himself to cleave enemies in two. He dodges Tsubaki's dead-serious questions with vague answers while his stomach aches, wishing the castle raid would end quickly.