One day, Haruma Kozai was suddenly transported to a town centered around a dungeon. The special skill he was given was [Summon Angel]. This skill with a mysterious name does not simply summon an angel - rather it's a slightly strange skill in which angels are summoned for a price.

...At least that's what he thought, but it seems like “pleasure” is the price to pay!? Make the summoned angel cum and decide on the cheat boost.