Yuichi lost his father when he was a kid. However, he now lives peacefully with his mother and younger sister. One day, his grandfather says to them, “Why don’t you live with me?” Like this, he starts living with his grandfather, but his grandfather’s purpose is to train him as his heir. He also orders Yuichi to make babies…. What will happen to Yuichi? Who will he make babies with? His new life now begins….