WARNING! Spoilers ahead for Blue Exorcist and The 8th Night
So, I recently watched a recap of a Korean Mystery-Thriller film called "The 8th Night". The basic premise is that a young monk and an exorcist must hunt down one of two malevolent eyes that Buddha once extracted from a terrible monster from Hell before sealing them away, before the eye can possess 7 people within 7 days and reunite with the other eye on the 8th, causing the monster's power to reawaken and threaten the world.
Upon watching the recap, I found it eerily similar to the events of The Impure King Arc from the anime Blue Exorcist. In this storyline, Rin Okumura (the series' protagonist and Half-Demon son of Satan), must stop an evil former exorcist named "Saburota Todo" from restoring a powerful Demon of Rot called "The Impure King" by returning his two eyes (later revealed to be the two halves of his heart) that were hidden by Buddhist monks after The Demon was defeated by one of their predecessors. As the one who now wields that legendary monk's sword, Rin is naturally the one who ends up having to stop The Impure King.
So, given the remarkable similarities between these stories, I found myself wondering if these stories are inspired by some tale in mythology or literature. But despite having studied Asian religion for a semester and looking all over the internet for answers, I still came up blank. So, is there anyone who can shed some light on this? Is there something from (I assume Asian) mythology that these stories are inspired by, or is it just an unbelievable coincidence?