Mithrun

Captain of the Canary Squad. 185 years old. A slender man with silver hair and black eyes. The criminals in charge of the guards are Cithis and Otta. His right eye is a prosthetic, and both ears are missing the upper halves. He has a poor sense of direction and occasionally tries to walk back the way he came. He has extensive knowledge of monsters and seems to be well-versed in the characteristics of individual creatures, with scenes in the main story where he showcases some of this knowledge.

A user of teleportation magic. He can teleport someone by merely touching them briefly. He describes this as "sending" them, but in reality, he is "exchanging" them with an object at the destination. During combat, he uses his ability in various ways, such as embedding an opponent in a wall, dropping objects on them from above, or swapping parts of an object with parts of the opponent's body to inflict injuries. However, due to being one-eyed and directionally challenged, he often misses the intended location of teleportation. He also appears to be capable of using resurrection, detoxification, or sleep magic. Despite his slender appearance, he has very high physical abilities, and when confronting the subordinates of the back island master, he overwhelms them using his teleportation magic, even though they are armed, while he is unarmed. When transformed into a human as a changeling, his crafted body is exposed, and Kabru comments on his "sturdy back." According to the Adventurer's Bible, he has made space in his small room for one-armed push-ups.

He is generally expressionless, with little emotional fluctuation. Leading the Canary Squad into the labyrinth, he corners the Mad Sorcerer using his teleportation magic but is stopped by Kabru. Afterwards, they fall deeper into the labyrinth and start acting together.

Originally the second son of a noble family, he became a guard and explored the labyrinth in place of his sickly brother. However, one day, a demon in the form of a goat tempted him with a future where he had not become a guard, leading him to become the master of the labyrinth. Eventually, the demon consumed almost all of his desires, leaving him unable to feel essential survival needs such as hunger, sleep, or excretion. The only desire left is his vengeance against the demon, which is now his sole reason for living.

He is aware of Sissel's background and history, as he had conducted prior investigations and knew that Sissel was of the same race. When Kabru mentioned that Laios loved monsters, he bluntly stated that it would be better to kill him before he became the master of the labyrinth.

Due to these circumstances, he harbors intense hatred towards the demon. When he caught up with Laios's group, he left their handling to the Pattadors while he searched for a book that sealed the winged lion. In Sissel's attic, he confronted Marcille and Izutsumi, but as Marcille did not know the true nature of the winged lion, their conversation did not align. He teleported the troublesome Izutsumi away and dodged Marcille, teleporting with her to rejoin the Pattadors. Misunderstanding Marcille as a high-ranking elf based on Chilchuck's remarks, Pattador and Marcille engaged in a conversation disguised as casual talk, which led to an interrogation to expose lies and resumed the search for the book. The search target was inside Marcille's clothes, leading Pattador to pull her away, allowing Marcille to release the winged lion. Despite his intense hatred and relentless assault, Marcille, declaring herself the master of the labyrinth and gaining power from the winged lion, subdued him along with the other Canary Squad members. Mithrun managed to escape using his teleportation magic but was knocked unconscious by Kabru, anticipating his severely injured state.

After awakening, he confronted Marcille, now the master of the labyrinth, and cornered her again, but was stopped by the winged lion and had his head blown off by Marcille's magic. In the main story, he became the only human Marcille killed.

Kabru had once predicted him to be a perfect young man, but Mithrun himself denied this, stating he looked down on all humans. However, his current relationship with his once-envied brother appears to be good.