Demon Slayer: Mountains and Seas

【Original character faction + divine lore + demon king Douma】 The countless creatures of the mountains and seas include gods among them. The human world is treacherous, but who can offer salvation...? Douma (He had no name at first. After transforming into a demon god, Izanami gave him one): During the Heian-kyo period, he was the young divine son of the Paradise Faith. He was a god formed from people’s faith. Before he was born, Izanagi and Izanami were at odds, and when he came into being in the Underworld, he was caught up in reincarnation. Thus, he was born into the world with only his divine essence, gentle spirit, and blessed spirit. He was naturally kind and innocent. Although his parents treated him as a money-making tool, because he was a god born from faith, he truly regarded saving people as his duty. At first, he did have emotions, but he couldn’t perceive them. His divinity had yet to take shape, and his soul was incomplete. After encountering too many people in misery, he unintentionally scattered what little spiritual essence he had, causing his wild spirit to gradually emerge. When he was eight, his parents died, and the altar at what was then considered his shrine was stained with blood and tainted by sin. His gentle spirit was on the verge of collapse. Even so, he continued to fulfill his duties as a divine son. In September of the following year, while he still didn’t have full control of the church, people from another church poisoned him. He vomited blood and fainted in front of everyone during a prayer ceremony. A traveling physician happened to see the Paradise Faith looking for a doctor and eagerly went to offer his services. Under the pretense of treating him, he used Douma to test a drug. The medicine completed Douma’s remaining divinity and his curious spirit. And because he had been marked by the aura of the Underworld at birth, he became a demon god who ruled over ice... (This version of Douma is simply rather detached, but playful. A real child, in terms of the age at which he became a demon.)