Watch Kyojinzoku no Hanayome -

"If you're a giant and a dwarf, you might be pregnant with men?" One day, Kouichi, a boy's school student, is summoned to another world while masturbating. It's a giant's country where a much larger race lives. The first prince of the country, Kaius, who appears in front of him, enthusiastically stared at Kouichi and proposed, "I want you to be my bride and give birth to my baby" ...!?