User blog comment:B214/Volume 22 spoilers/@comment-83.27.153.180-20160721093944/@comment-24.113.252.213-20160721184446

Maybe Bina Lessthan (Issei's Masked Queen) is actually an "agent" of the remaining decendants of the Original Satans, and they sent her to see what Issei is actually like as a person, and his potential as a King. If Issei does well, the Original Satan's decendans might reveal themselves and give Issei their support (in whatever way that is, I don't know). So either Bina is a member of the Original Satan's decendants, or she is from a family of Extra Demons that serves them. In either case, she would need to wear a mask so the public or higher-ups don't catch on.