Seiju Shinano

He is Mayuki's father. He's the former head of the Hyuuga family before Mayuki. He's born in the Shinano family but because of his extrasensory perception, the Hyuga family adopted him to have an heir. After Mayuki was born, he became nothing. Because of that, he did bad things. He is jealous of Mayuki because he wanted Mayuki's power.

[Spoiler] He's Seiran and Shien's brother in reality. He's also a doll user. [/Spoiler]

(Source: Wikipedia)