Aika

Aika is a Summoner belonging to one of the Three Great Summoner Powers, "Government," she is a shut-in who idolizes Kyousuke Shiroyama, affectionately calling him "Onii-chan." She as a pet white liger which she uses as a yorishiro.

(Source: Mitou Shoukan://Blood Sign Wiki)

[Spoiler] Her full name is Aika Toydream. [/Spoiler]