Kerioil is a man who appears in the anime Reborn as a Vending Machine, I Now Wander the Dungeon. He is easily recognized by his cowboy-style clothing, which includes a cowboy hat, a vest, and fingerless gloves, and he has orange hair and grey eyes. He serves as the leader of a party known as the Fool's Oddities Brigade, though this group is later revealed to be a family unit composed of his wife and children.

In terms of personality, Kerioil often displays an arrogant and flippant demeanor. He has a tendency to delegate undesirable tasks to other members of his group and engages in playful banter with them, indicating a dynamic that is generally good-natured despite his leadership style. Beneath this surface, he is shown to be a caring individual, particularly when it comes to the safety of his family and allies. He also has a less admirable trait of being somewhat lecherous, an action for which his wife scolds him.

Kerioil's primary motivation is centered on his family. A significant driving force for his actions is the condition of his unnamed eldest son, who suffers from a curse that causes the corrosion of his flesh. This affliction is slowly killing the boy, and Kerioil seeks a way to save him. To this end, he enters into a secret alliance with a powerful entity known as the Netherlord, who promises to help save his son in exchange for Kerioil's allegiance. His role in the story evolves from a potential ally and rival hunter to a more complex figure caught between his familial duties and his agreements with antagonistic forces. His party's goal is to collect Lord Coins from powerful floor bosses, as these coins are said to grant wishes when used in the deepest part of the dungeon, and he hopes to use them to cure his son.

Key relationships define much of his character. He is the husband of Filmina, a composed and cool-headed magic user who serves as his second-in-command and often provides a calming presence to counter his impulsiveness. Aka and Shiro are his twin children, who are also members of the brigade. His relationship with the protagonist, a vending machine named Boxxo, and the powerful hunter Lammis is complex. He recognizes Boxxo as an indispensable asset for his party's goals and attempts to recruit them. However, his trustworthiness is called into question during an incident where he is forced to temporarily leave Boxxo behind to battle a floor boss, the Eight-legged Crocodile. This decision results in Boxxo falling to a lower level, and when Lammis regains consciousness and learns of this, she furiously confronts Kerioyl, forcing him to help her retrieve the vending machine. This event strains their relationship, and Lammis later turns against him upon learning of his true intentions with the Netherlord.

Throughout the narrative, Kerioyl undergoes development that reveals the depth of his character. While initially appearing as a somewhat lazy and arrogant leader, his actions are progressively shown to be driven by a desperate need to save his son. His secret pact with the Netherlord, which at first seems like a betrayal, is later framed as a tragic choice made for his family. When his ulterior motive is discovered, most of his team turns on him, highlighting the consequences of his secretive path. However, later events in the story suggest that Kerioyl and his family care more for Boxxo's welfare than they let on, with his wife even whispering a warning to Boxxo in a dangerous situation, and the family may be secretly working to undermine the Netherlord from within.

Kerioyl is a formidable fighter specializing in close-quarters combat, demonstrating great skill with knives. He is described as an excellent swordsman as well. Beyond his physical prowess, Kerioyl possesses a secret ability that allows him to disable the blessings of others, which is notably effective against individuals like Boxxo and a hunter named Hevee, making him a particularly dangerous opponent in a world where such blessings are common.