Satan fathered twins in the human world, and now one of them is trying to become an exorcist to kill his own father. The chemistry between Rin and Yukio carries you through the early episodes on pure character momentum. The show loses its way once it abandons that premise for filler, but those first arcs prove the core idea had real weight.

Rin Okumura seems like an ordinary, somewhat troublesome teenager until a demon attack turns his life upside down. He learns that two mirrored worlds exist side by side: Assiah, where humans live, and Gehenna, the realm of demons. Contact between them is normally impossible, but demons can cross over by possessing things in the human world. Satan, ruler of Gehenna, has no host strong enough to hold him, so he fathered Rin with a human woman, meaning for his son to grow into that vessel so they can conquer Assiah together. Rin refuses. He chooses to train as an exorcist and fight to protect Assiah alongside his brother Yukio, in a supernatural action fantasy based on Kazue Katou's manga.