Tsui no Sora

When Yukito and his childhood friend Kotomi show up to school on an otherwise ordinary Monday morning, they're greeted by a dead classmate, rumors of the apocalypse, and the quiet kid who used to get bullied who has somehow decided he's a messiah. Tsui no Sora is a single-episode OVA adapted from the visual novel by KeroQ, and it leans hard into psychological horror and existential dread rather than anything comfortable. The school setting starts normal enough, but it deteriorates fast — the kind of slow unraveling where you're not sure if the world is ending or if everyone has just lost their minds, or both. There's a genuinely unsettling atmosphere here, built around questions about death, belief, and what people are capable of when panic sets in. It's not a long watch, but it's dense. If you've seen School Days and appreciated how a school drama can go somewhere genuinely disturbing, this scratches a similar itch. Fans of Yosuga no Sora who want something heavier in tone might also find it interesting. Just go in knowing it's a hentai OVA with actual horror framing — it takes the darker themes from its source material seriously, which makes the whole thing feel stranger and more unsettling than you might expect from the format. Worth it if you're in the mood for something bleak and weird.