Hyakki: The Secret of Devil's Island

Headed for a long-abandoned island — once a real city, now just crumbling buildings and overgrown streets — a tour boat carries a handful of young adults toward something none of them fully understand. Everyone has their own reason for going: some grew up there, some are just chasing the thrill of exploring ruins. Seems like a moody little adventure at first. Then people start acting strange, old memories claw their way back to the surface, and the island starts feeling less like a destination and more like something that wanted them there. Hyakki is a 3-episode horror OVA from Arms, adapted from a visual novel, and it leans hard into atmosphere. The decaying urban setting does a lot of heavy lifting — there's something genuinely unsettling about a place that used to be full of people and just... isn't anymore. The horror builds slowly rather than jumping straight into chaos, which gives the character tensions room to simmer before things unravel. Fair warning: this is a hentai title, so the sexual content is part of the package, and it's woven into the psychological unraveling rather than sitting completely separate from the horror. That blend is either going to work for you or it won't. If you've watched Requiem from the Darkness and liked how it made atmosphere do most of the storytelling, or if Ghost Hunt's slow-burn dread is your thing, Hyakki scratches a similar itch — just with a much darker edge and adult content layered in.