Adult PC Game: Tears to Tiara by Leaf Archive

The priestess Erina, a Gaelic god, must become a sacrifice for the resurrection of the formidable deity Aruan, whose wish is to destroy this world. Her brother Arthur rushes to her aid, but he fails to prevent Aruan's resurrection. However, the suggestive nightmare god himself, seeing in the girl something other than a victim, rises to the defense of the priestess of the Morning Star.

Tears to Tiara by Leaf Gameplay Preview