The Other Shore at Dawn: Unfinished Wish

A word of warning: This story comes from the fantasies I had as a child. Although it's GL, it isn't just about the romance between two people, and it has absolutely nothing to do with real life. If you're looking for a lighthearted romantic comedy, proceed with caution. Also, this story is an endless pit, though the author is determined to finish it... So... in short, please proceed with caution. Here's the actual introduction:

In 20XX, the awakening of the Demon King brought Hell to Earth ahead of schedule. The armies of Heaven were utterly defeated, and the demons seized the entire world above. Their arrival also brought many previously unknown races into the open. Humanity retained some technology, but society as a whole regressed drastically. In short, the world became much like an ordinary fantasy setting... Then, more than a thousand years after the demons conquered the world above, a child appeared (though not a child for long) ^ ^