Masquerade

Following the death of his parents, Gen Hiraga moves into his grandmother's secluded estate, which sounds like a quiet, melancholic setup — until he accidentally wakes up a centuries-old curse that's been quietly killing off members of his bloodline for generations. From there, the show leans into occult mystery territory, following Gen and an American graduate student as they dig through the estate's shadowy corners, trying to piece together fragmented dreams and whispered family legends about immortality. There's a genuine ancestral thriller running through all four episodes, and the curse lore has enough hooks to keep you curious about where it's all heading. The tone mixes eerie supernatural atmosphere with moments of comedy, so it never gets relentlessly grim, though it does carry mature content throughout — this is a hentai OVA, so factor that in going in. The retro cel animation from AIC leans into moody, dimly lit environments that actually suit the mystery pretty well. If you've watched something like Nightmare Campus or Bible Black and appreciated when those titles bothered to build atmosphere around their adult content, Gosenzo Sane scratches a similar itch. It's a short watch at four episodes, and the story stays focused on the estate mystery without sprawling too far. Not a hidden masterpiece, but a solid late-90s OVA that puts in more narrative effort than you'd typically expect from the genre.