Onmyouji: Youen Emaki

When a series of gruesome murders begins plaguing the capital of ancient Japan, nobody can figure out what's doing it, so Abe no Seimei gets involved. He's an onmyouji, essentially a master of occult arts and spiritual rituals, and when bodies start turning up in ways that don't make sense for any human killer, he and his companion Hiromasa start pulling at the thread. What they find points straight to demonic forces lurking beneath the surface of the capital. This 2-episode OVA from 2003 blends historical Japan with supernatural horror in a way that feels genuinely atmospheric. The onmyouji rituals are depicted with some care, and the mystery framing gives the whole thing a suspenseful, investigative quality before it leans into its darker content. The ancient setting and mythology-heavy backdrop give it texture that a lot of adult anime from that era skips entirely. Fair warning going in — this sits firmly in hentai territory, so the supernatural horror and the explicit content are woven together throughout. If you've seen things like Bible Black or La Blue Girl and appreciated how they at least tried to build atmosphere around their premise, this scratches a similar itch. The historical folklore angle makes it feel closer to something like Dororo in terms of setting inspiration, just taken somewhere very different. Two episodes means it's a quick watch, and the demon murder mystery framing keeps things moving.