Miki Rintarou

Miki Rintarou is a supporting character in A Terrified Teacher at Ghoul School. He is an oni, and a teacher of youkai studies at Hyakki Academy.

Appearance
Miki has light teal hair that reaches a bit past his jaw. In some official art, his hair appears light pink or white. He has a horn on the right side of his forehead. Miki's right eye is blue, and he has a beauty mark right under it. His left eye is usually covered by his hair, and underneath it is black with a blue pupil (Sans Undertale Moment). He often wears a button-up shirt with a waistcoat on top.

Miki is often complimented for his looks, and he can look very feminine at times. Up until grade school, he thought he was a girl.

Personality
Miki is often flirty and smiles a lot. He doesn't seem to take most things too seriously, and he's often late with his paperwork (such as creating exams). When he's teaching, he's firm with his students. Miki enjoys drinking, and his personality turns aggressive when he's drunk. Miki can also be very cunning, even to the point of using people close to him to achieve his ends.

Miki bickers a lot with Hatanaka Izuna, and the two are close friends since their school years. He seems to enjoy causing trouble for others especially when he's with Hatanaka.

Powers
Miki is an action type youkai, which means a specific physical action gives him spirit energy to use his magic. In Miki's case, drinking alcohol invokes his powers. which makes him grow exponentially stronger. However, he gets drunk very easily (even from non-alcoholic drinks), so he usually loses control when activating his powers.

Up until he was old enough to drink alcohol, he was basically a human with a horn.

Abe Haruaki
At first, Miki and Haruaki are simply co-workers. Later on, they two become friends after Miki, Hatanaka and the principal console Haruaki when he's feeling down.

In Volume 8 it's revealed that Miki doesn't actually consider Haruaki his friend. He keeps Haruaki close as Haruaki has the powers of Abe no Seimei, which can help Miki get rid of his mother. If Haruaki didn't have such powers, Miki would never be friends with a human.

Miki later feels touched by how Haruaki is determined to help him. He thanks Haruaki for his help, and the two officially become friends.

It is then revealed, that the two met while they were children, and Miki's mother caused an accident of the same kind as previously in the chapter. This event stuck to Miki, and he didn't want to make friends in fear of the same thing happening again.

Hatanaka Izuna
Miki and Hatanaka have been friends since their school years. The two are often together, and they bicker a lot. They usually call each other by their first names only when they're not at work.

Hatanaka often scolds Miki for being late with his work. In return, Miki teases Hatanaka for his past as a delinquent showing when he's angry. When they were younger, they played pranks on their homeroom teacher. Even as adults, they still like making trouble others.

Trivia

 * Rintarou thought he was a girl until primary school/grade school