How did I, an Onmyoji, become the Lord of Yokai?

Synopsis: Asahi Shimizu, who was raised by a yokai (god), has a dream.
He hopes that humans and monsters can put aside their prejudices against each other and live in peace.
Driven by this dream, he diligently cultivated his skills and studied hard. After graduating from the Yin-Yang Bureau, he devoted himself to solving problems for both humans and yokai.
Finally, twenty years later, looking at the oni queen Takiyasha-hime, the oni king of Mount Oe Ibuki-dōji, the daughter of Mount Suzuka Suzuka Gozen, and the master of the Hundred Tales Aoandon by his side, he couldn't help but sigh that his dream had come true.
But why are other Onmyoji starting to call him the Lord of Yokai?
(Onmyoji fanfiction, mixed with Nurarihyon no Mago characters and FGO characters)