This island was uninhabited for many years, maybe even for hundreds of years, but one day, a pirate ship was stranded on it. From the records I could find, there were only 47 people abroad. Though the majority of the crew were human, some were youkai - for pirates, the strength is in numbers and they can't afford to discriminate. Though it should be noted that the crew members were criminals and low-lifes.
One of the most notable people was the crew's captain - who is ironically shrouded in mystery. No one seemed to know where he came from, he just appeared in the crew's life, stating that he wants to "liberate the forgotten". And his activity is also pretty much hard to track down, with all the remaining records pretty much praising the captain who was "swift as Isonade" due to his skills as a skipper who drowned many rivaling pirate ships. That's why he is referred to as "Ayakashi", due to his skills being almost, if not on par with a powerful youkai.
After his crew settled on this island after an unfortunate crash caused by mirages (likely Fata Morgana; though it was described as "wondrous city made of scales" and that the captain looked at the mirage with sense of nostalgia), they noted that the thick fog was surrounding the island, which also contained various hallucinations. And during the moment of despair, the captain has calmed his crewmates down with his mighty voice and cast the fog away. He was revered as a hero and was essentially deified, making his children the nobles. He lived to the age of 97 (though it was implied to be more) and his youngest son has become the first priest of "Kirishima(霧島)" and the deified captain became known as "霧島の神(Kirishima-no-kami)" or "大海乃神(Wadanojin)" or even "津波樓(Tsunami-Takadono)". He was described as a benevolent God who always watched over his envoys (priests), especially when they're still young - acting as a guardian figure.
However a tragedy struck when the 13th generation priest - "Wadano no Tenmuyonji (大 海乃の天無四時)" was executed by hanging due to not fulfilling the order to kill halfamanojaku, half-human baby (which resulted in a failure to save Urime (瓜芽) from the intruder), instead opting to adopt them as their heir. By that point, the influence of Wadanojin was dwindling with the arrival of new stranded people who overthrew the "old guard" and none of them saw any issue with executing the final branch. This not only angered Tenmuyonji themselves (who became the vengeful spirit known as "霧島の祟り 神 (Tatarigami of Kirishima)"), but also Wadanojin as well, causing the island to become foggy once again.
Soon the Wadanojin became known as a very violent and malevolent God who requires a human sacrifice every year in the form of "prayers" - people who get stranded on this island. He is less known than Tatarigami, but it is an accepted fact that Tatarigami is a servant of Wadanojin.
I saw him (or rather his apparition) when I was drowning in the sea... And now I'm obsessed with him.
Did he truly die back then? Was he some sort of yokai? What was his past life? I can't seem to find the answer.
Either way... That person... Is not normal. It feels like an anomaly of its own.
- Sunao Fujisaki (藤崎・巣菜御)