Gunpei is just an average student. He just lives in a small town and lives a peaceful life. But one day, two girls suddenly visit his house. They are actually from a small country in the Atlantic Ocean, Chiha, a princess, and Tigarna, her follower. The purpose of their visit is to make him the crown prince of their country. Gunpei is, of course, surprised to hear that because he is just a citizen.

According to Chiha, Gunpei's father is a soldier of her country and prevented terrorist attacks or saved the royal family many times before. His intelligence, power and warm personality are loved by every citizen. King thought of accepting him as his daughter's husband, but he was already married. How about his son? His excellent gene must be inherited to his son! Chiha says, "Please make me pregnant within six months." "What!?" Like this, his life dramatically changes...