欢迎来到性爱开放的世界！

Welcome to a Sexy, Open World
A brand new title from MOONSTONE Cherry, the creators of Imouto Paradise - Welcome to a Sexy, Open World!

When the young Sejima Seiya tries to rescue a dog, the passing truck winds up sending him straight into a completely different world! In this brand new world, Seiya finds himself caught up in an ancient prophecy that someone from another world will arrive to give birth to the legendary heroes that will end the wars plaguing the lands. What is Seiya to do as key women from every major nation in this new world start accosting him for his baby batter in an attempt to ensure their nation holds the most influence over the heroes destined to be born?! Worse yet - even if Seiya wanted to avoid becoming a stud, it turns out that if he doesn't create a child to bind his presence in this new world, then he'll be pushed out of it and sent back to the moment of that fateful accident! Luckily for the unwitting father of heroes, coming to this world has given him the power to know when a woman is at her peak fertility!

Description
When he awakens from a terrible accident, Sejima Seiya finds himself in another world—Laurentide.

A world with a legend, long held by its people:

──The seed that shall give birth to heroes and end the era of war shall come from another world.──

Seiya has that seed within him.
And despite being viewed as breeding stock, he still wishes to have sex.
But now the father of the future heroes could become king of the world.

So...

Drawn by the legend, beautiful women gather from across the world, seeking his seed.

──Or perhaps some harbor the ambition of unifying the world under their motherland.
──Or perhaps some simply desire sex with Seiya.

Regardless, Seiya's days of getting milked by beautiful women have begun...

[From MangaGamer]