This is trying to poach from Aa! Megami-sama! but fails to do so,because it's focused too much on the cute/moe appeal.
All love but gods is temporary, this is the rule of the world, so I don't know how they attempt to spin this into drama every. single. time.
It's strange how people come up with pedophilia in this context. Pedophilia is a concept of age of consent that has been violated.
It doesn't apply to a society that doesn't have individual rights to begin with, as in this case a child became a slave,which is impossible unless the parents know no concept of individual rights either, which they would have to guard until their child is of age.
In fact, the very status of a "child" is nothing more than a peculiarity of European culture, it doesn't even apply everywhere on the planet earth.
We are looking here at two different societies with different states of development, philosophical education (if there is any at all, people who work all day to make a living don't have the luxury to entertain such abstract concepts at all), mental capacities (yes, the ability to think in abstractions is not equal even on planet earth, there are cultures, especially in Africa, that are unable to understand abstract concepts they cannot see, even including what could be happening to them in the future) and bodily ability in one story (the so-called "demons" and the so-called "humans") that interact in this story.
Now I wonder, how they can even come up with this story, since demons(they are purely spiritual beings) don't have a body while humans have one. How could they touch and/or even interact with each other through other means than possession?
And even if we grant the author the mistake of definition or the translator the mistake of mistranslation (since the Japanese "ma" is not equal to a European Demon), there would still be the issue of genetic discord. Unless both species developed from the same line and spread out after about 4 or 5 million years ago, it would be impossible to procreate, and even then it would still be questionable if the offspring was fertile.
This story goes nowhere trying to elucidate how this would be even remotely possible, with some radically different explanation like "every being is formed by a god and can thus interbreed;there are no genes, and offspring is created by means of the gods as well(e.g. by extracting a part of the fathers and the mothers soul,mixing and magnifying it,then adding it to the created body), delivered to the earthly realm via teleportation into a temple or whatever".
Japanese fantasy fails at the most basic step( world building) and yet people are hounding down the fact that the female MC took in the male MC and is going to "marry" him (again, the Japanese term "kekkon" is not equal to the term marriage, it has other implications),coining it as pedophilia.