Status: A hunter boy from 'Higashimura,' a village deep in the mountains. Family: Twin sister Asa. Contracted Tsugai: Left and Right. He is the older brother of the special twins who can shake the balance of the world. Yuru possesses the power of 'Seal' (封), which allows him to bind and dominate all things. Raised far from civilization, he is highly skilled in archery and hunting. He demonstrates a strong mental fortitude and cold judgment that remains unshaken even in crisis situations. After the village is attacked, he descends to the Lower World (modern society). He shows a quirky yet rapid adaptation to modern culture, such as smartphones and cars.

Appearance: A girl with a sharp impression, long black hair, and an eyepatch over her right eye. Family: Twin brother Yuru. Contracted Tsugai: Yin and Yang. Born with the power of 'Release' (解), the opposite of her twin brother Yuru's 'Seal' (封). This ability is a powerful and destructive force that can forcibly open any closed barriers or seals and break the Tsugai contracts of others. She first appears as a mysterious intruder attacking Higashimura, where Yuru lived. She caused great confusion for Yuru by killing the 'Fake Asa' imprisoned in the village jail and revealing herself as the real sister. Although she appears to be a cold and tough survivor on the outside, she deeply cherishes and loves her brother Yuru. She shows a 'gap moe' side, shedding tears or reacting like a passionate fan seeing an idol when in front of her brother.

A beautiful boy with short blonde hair and striking purple eyes. Despite his small and cute appearance, his true identity is a monster with powerful strength. Usually innocent and lively, he radiates a cold and overwhelming aura during combat. This stark contrast and mysterious atmosphere are the core characteristics that define Gab. He commands the Tsugai named Gabriele. When he says 'Bite' to Gabriele, the Tsugai attacks.

A Tsugai in the shape of a giant jaw split into upper and lower parts. It is characterized by a bizarre appearance embedded with countless eyes; it is usually small but grows massive during battle. It possesses terrifying cutting power that can crush and chew through anything. It has absolute defensive capabilities, blocking physical attacks by closing its jaws. It is a threatening presence that switches between offense and defense according to the orders of its master, Gab. It floats like a ghost without arms or legs.

Appears as a female ogre with a single horn, wearing Oriental-style clothing reminiscent of a Hanbok. Behind a blunt expression, she has a warmth that cherishes the protagonist (??), and she subdues enemies with overwhelming physical strength and martial arts. She is most powerful when fighting in sync with her partner, 'Right'.

Appears as a sturdy male ogre with two horns on his head, wearing Oriental-style clothing that contrasts with 'Left'. Unlike the blunt Left, he has a lively and bellicose personality. Based on his incredible defense and tenacity, he overwhelms enemies from the front. He is a reliable supporter who boasts perfect chemistry with his partner, 'Left'.

Yuru's ally, a 35-year-old man. He has a seasoned appearance characterized by hair tied back, a beard, and glasses. While he appears to be a sly traveling merchant on the surface, he is actually the head of the Tadera family that protects Yuru. Although he cannot command Tsugai, he can see them. A reliable guide who helps Yuru adapt to modern society and combat with his wealth of experience and insight. He is skilled with guns.

A Tsugai user from the Lower World who helps Yuru. Appearance: Short light brown hair, usually wearing comfortable tracksuits and carrying metal knuckles. Characteristics: She is clever and strong-willed, and the master of 'Zen-go-ko-ro,' a Tsugai specialized in information gathering. She is skilled in hand-to-hand combat and driving.

Appearance: Primarily has a black body and a white face, with the Yin (陰) symbol of the Taegeuk drawn on its face. It usually flies around Asa in a miniaturized form. Characteristics: During battle, it merges with Yang to become giant, exercising a unique ability to trap targets in a boundary space of infinite darkness where not even a single finger can be seen.

Appearance: Primarily has a white body and a black face, with the Yang (陽) symbol of the Taegeuk drawn on its face. It usually floats near Asa in a miniaturized form. Characteristics: During battle, it merges with Yin to grow massive, neutralizing enemies by exercising a unique ability to trap them in a blindingly white and vast boundary space.