Avian Wander

Frederica, the older sister. She contracts a demon, hunts the souls of the wicked, and sends them to hell. She is the silver seal.

Howly, the younger brother. He was given his life by a demon, according to his sister's wish. He serves and protects the silver seal. He is the warrior seal.

What will the world give to them...

(Source: MU)

Included one-shot:
Volume 2: Aegis to Sono Shugosha (prototype one-shot)