Aoi Masamichi, who became a doctor in order to save Tachibana Mai, his childhood friend and lover who ended up suffering an intractable disease, gave it his everything to search for a cure. However, it went unfulfilled, and he ended up losing her. Aoi, who fell into despair, ended his own life and followed Mai’s footsteps. He intended to die, but when he woke up, it seemed he ended up reincarnating into an Otherworld. And with the memories of his previous life for some reason at that. And then, it was an Otherworld that was like Japan but wasn’t Japan. In that somewhat strange world, the newly-born Aoi was informed of a shocking truth by his grandfather. It’s difficult to have a child in that world, and amongst them, they only have a boy at a 1 to 5 ratio. And ‘you were born as the heir to a family of Gods’. Furthermore, he wants him to unravel the reason it’s difficult to have a child in this world and lead the world to have plenty of boys. He ends up accepting it despite being perplexed at being given such a request. Without knowing whether Mai has reincarnated into this world with himself, Aoi, who has lost his reason to live, sealed off that sadness and took on the challenge of not just the birth rate problem, but the unravelling of this world’s mysteries as well.