One day, a male high school student Koichi (180 cm) is summoned to another world when he was masturbating. It is a country of giants, where a species much larger than him live. The first prince of the country, Kaius (250 cm), looks at Koichi enthusiastically and makes a proposal of marriage to him, "I want you to be my bride and give birth to my child." (Source: Crunchyroll)