Gaako

Gaako is a freshman demon who attends Babyls Demon School, the same school of the protaganist, Suzuki Iruma.

She is a short pudgy green dragon with purple eyes. She has three horns on the top of her head with one horn being located on her forehead and the other two on the back of her head. On the sides of her face, she has three spikes. On her back, she has two small light green wings. She has sharp fangs that are seen when she opens her mouth. She has six blue spikes with two located on the back of her head and four on her tail. She is seen wearing the school female uniform.

She is also Eiko Oni's best friend who attends the same cohort.

(Source: Mairimashita! Iruma-kun wiki)