3Ping Lovers! ☆ Ippu Nisai no Sekai e Youkoso♪

Kutsuki Tomohiro is the protagonist, a male student who admits that he has nothing special to offer.
One morning on his way to school, he is unexpectedly enveloped by a blinding light and loses consciousness.
When he wakes up, he finds himself in a place he has never seen before.
"Where is this......?"
Two girls are standing in front of Tomohiro's confused eyes.
The girls tell him that they had used magic to summon him to a fantasy world.

He's suprised to hear that, and even more when they say that he, who previously thought to had nothing special in him, was actually born with a hidden special ability.
That is... Tomohiro's semen has the effect of increasing magic power!
The girls who fight the monsters that attack people need strong magical power, and they ask Tomohiro for semen to increase their magical power.

And in this world, where chastity is highly valued, once you have sex, you must get married, and both girls want to get married.
Yes, in the fantasy world, one man marrying two women, "polygamy", is the norm.
In a fantasy world where everything is out of the ordinary, Tomohiro's newlywed life and battles begin now...!

[Modified from Getchu]