Adult PC Game: Gada Musume Quest by sweet princess Archive

The world of Meiria was populated by
the goddess Alice who created humans and
the demoness Gadalf who created monsters.

.. but you can disregard the history of things. LOL

Essentially, to rid the world of the monsters,
a guy from the world of Earth is to Meiria!
His name is Shiotaro. Gifted with the power of a sex god,
his charge is to wield that power on the monsters.

The one who summons him teaches him how to screw,
and how to battle monsters with his sexual talents.

Shiotaro's orgasms are gush upon gush
as the so-called sex god is drawn into "war".