Shin Reglia

First appearance

Anime: Episode 5

Light Novel: Volume 2

Shin Reglia is the right-hand man of the Demon King Anos Voldigoad and the most powerful swordsman among the demons.

[Spoiler] He is the husband of the Great Spirit Reno, and the father of their daughter, Misa. He became the Spirit King after Reno's passing and founded the Unitarians to create a better place for Misa due to her mixed-blood status. [/Spoiler]

(Source: Maou Gakuin Wiki)