There are 3 separate powerful kingdoms: Kingdom A, Kingdom B, and Kingdom C. A dragon who belongs to Kingdom A just flew past the border of Kingdom B coming from Kingdom A and is carrying 2 adult citizens of Kingdom C. The two adults, a man and a woman, are citizens of Kingdom C and they literally just gave birth to a child. Every kingdom wants to get the child because, well it is an Isekai story, and the child is, of course, the reincarnation of a Jap guy that just got killed by truck-san and is destined to become an OP MC. So, who should own the kid? Kingdom A, because the baby is born on top of the dragon and the dragon is the property of Kingdom A and therefore the baby is born in their land. Kingdom B, because the destination of the baby is kingdom B and technically, since the dragon pass the air space of Kingdom B, then they are in the territory of Kingdom B and therefore the citizenship of the Baby should be Kingdom B. Or Kingdom C, because, well in the first place, both parents are from kingdom C, so citizenship of the baby goes to them.