Parallel World Wife Swapping

A game where heroines from five previous works get swinging in a new world!

Kousuke and Ai have been dating for a year now.
But as they're going at it, a light envelops their bodies!
When they open their eyes, they find that they've been transported to another world... along
with even more people. The only way back is sexual energy, but where does that come from?
Take a guess!