守護天使強制発情！ ～人外の快楽に溺れる戦乙女～

Ruix (protagonist) was the highest ranking demon of the underworld.
Repeatedly, he plundered the Earth for fornicating humans, in an attempt to change the world into a farm of sinful copulation.
No matter how often he invaded Earth, however, a single angel stood in his way.
She was Mikaela, the highest ranking angel of heaven.

===== An Epic Clash of Good & Evil, Lust & Purity! =====