You know, this is pretty standard for a author that does h-manga, just check EBA and Ohmi Takeshi works. Few h-manga authors do proper manga with a actual plot and leave the h-manga circle, like Maybe and Amazume Ryuta.
@Ainz I don't think it went into his life on Earth, so there's a decent chance he has friends and family he misses. He may even already be in a relationship.
Plus, there's fewer modern amenities.
Although, what confuses me is why he didn't ask them to come with him. Even if he didn't give them children, there'd be tons of options for them if they went to Earth.