Seikou Tenshi Noel - Akuma no Kokuin to Mugen Ingoku

The protagonist Noel is a laid-back, ordinary girl. One day, she’s saved by a mysterious angel and granted the power of the “Holy Light Angel.”
However, she’s also marked with a “Demon’s Brand,” which causes her body to lean toward demonic corruption the more she experiences pleasure. There’s even a risk she could fall from grace and become a servant of the demons.
Despite this, Noel decides to push forward with the “Demon’s Brand” for the sake of peace, aiming to defeat the final boss, the sorcerer Phallus.

[Translated from dlsite]