Reishin

Reishin is Kuro brother. He has black hair and disposes a lot of tera. He is known to be the most powerful Tera guardian. He made a contract with Yuki Kaionji, but after she died, he decided to make Akane to be his contractee. He kills all his tribe to protect his sister and try to make himself the antagonist of the story. He destroyed all the cristal, who have a link with the Kamasagi, to prevent the awakening of his sister's real nature and power that hide in her body. So he decided to kill the Kamasagi with the help of his new contractee, Akane (In the anime).

After that, he sacrificed himself to protect Keita against the Kamasagi. He relinquished his last power to seal the regeneration of the Kamasagi and passed away after the battle.

Kuro
He is kuro's brother. He is very gentle and loves his sister very much; to the point of protecting her and to break the Kamasagi curses upon his sister and the world, both Human and Tera guardian.

Keita
He thanks Keita to help his sister to recognize herself during the Kamasagi possession in her body.

Yuki Kaionji
He is her contractee and her lover. He is deeply in love with her. We can see that in the anime, he hugs her tightly.

Akane
After Yuki's death, he decided to make Akane his contractee to help him to destroy the Kamasagi. He chooses her because she is the most powerful Master root who can beat the Kamasagi. He has no feelings towards her, but just as friend.