The Demon Lord himself. His sorrow seems to be so deep, it rains wherever he goes, but at the Demon Lord’s Castle, it felt increasingly oppressive. As if it had never stopped raining there.
His origin might be the first human, angry at the gods for taking away his wife. Because the theory is that when god made man and beasts, man was more intelligent, and did not want to live with the animals. They made him a woman as a companion, but to the gods’ she unexpectedly got pregnant— created life. The beasts saw, learned, and copied. The creation of life was something only gods should have, so they punished her and took her away after she gave birth, never to be seen again. This is the original sin, and why women are second class to men— why only women can be healers, to repent.
On the Demon Lord himself, I think he gets lonely and wanders into human society to observe them. Like a bored child watching ants run about. Originally, he only visits the bar and drinks, but at Haru’s advances, he enjoys talking to her and becomes an infrequent regular. When he learns about her power, he takes a 180, and declares that it’s her turn to come to him.
When she finally arrives, she doesn’t give him the death battle he seemingly desires, but instead they fuck, and she gets knocked up.