Ukobach

Ukobach (ウコバク) is Mephisto's familiar and a stove spirit who prepares Rin and Yukio's meals. He developed a close bond with Rin through their mutual love for cooking. He only appears in the anime.

Appearance
Ukobach is a satyr-like Demon, appearing mostly in the form a cute little imp. He can transform into a larger minotaur and appears from thunder strikes for comedic effect. He has yellow eyes.

Personality
Ukobach is proud of his cooking skills, but also fiercely protective of his food and his domain, the dorm kitchen. As such he was enraged at Rin for using the dorm kitchen without his permission and for a while he refused to cook for the brothers. However, he bonded with Rin over a cooking battle, finding his skills equal to his own; together, they make the ultimate lunches. More than anything, Ukobach likes to make people happy with his cooking skills.

He is shown not to tolerate the food he cooks being disrespected. When three girls infatuated with Yukio break into the kitchen to sneak the lunches they made for him in the refrigerator, they toss out the lunch Rin helped Ukobach make under the mistaken assumption that it was made by Shiemi for Yukio. In retaliation, Ukobach attempted to cook them into a stew. However, Rin was able to convince Ukobach that it would be a bad idea as the "meal" wouldn't make any who ate it happy.

True Cross Academy arc
Rin and Yukio find that the one responsible for their meals at the dormitory was Ukobach, a cooking familiar appointed by Mephisto Pheles to aid them. Later, Rin befriends Ukobach for their interest in cooking. But the brothers learn how Ukobach can be troublesome when he gets angry.

Anime-Exclusive arc
He appears again when Ukobach helps Rin and Konekomaru bake a cake for Izumo's surprise birthday. He shows Yukio and Rin that Christmas and birthday cakes are different.

Powers & Abilities
Expert Chef: Ukobach has incredible cooking skills, and is able to prepare delicious meals for both humans and Demons.

Enlarged Body: Ukobach has the ability to enlarge his body, giving him greater strength, similar to Kuro's ability to change from a small cat to a nekomata.

Ao no Exorcist Movie
Ukobach makes several cameos during the movie, all of which take place in the kitchen, where he has back turned to the camera.

Trivia

 * Ukobach is featured in Jacques Albin Simon Collin de Plancy's Dictionnaire Infernal as a demon responsible for inventing fireworks and frying foods.