The Name of God

Sengoku was a period when Japan was in war, a period when humans were still able to communicate with Gods. Young Sarutahiko has died because of the struggle, but he will be resurrected and turn into an immortal thanks to a God's power in exchange of consuming his sister's life day by day. To save her, Sarutahiko will ask for help to the God of the Mountain, but instead, he meets a beautiful young girl... What is the true identity of this girl?! What kind of God is capable of granting wishes in exchange of souls, blood and death...?!