Hentai Express

When a rogue professor steals a supercharged train and starts terrorizing a city, the only way to stop him involves a very unconventional energy source. That's the setup for Inyoku Tokkyuu Zetsurinou, a one-episode OVA from 2007 that mashes mecha sci-fi concepts with explicit adult content in a way you genuinely don't see often. The world runs on something called the Oraga Stone, which powers cyborgs and can tip the balance between good and evil. The catch is how you recharge it. Professor Saginomiya, once on the right side of things, goes off the deep end after getting his hands on the stone, hijacks the M-77 Express, and starts using it to fuel his own dark agenda across Blue City. The good guys respond by deploying their own train — the Sex Desire Express Zetsurinou — to go head-to-head with him. The premise is genuinely absurd in a pulpy, over-the-top way that commits fully to its own logic. If you've watched things like In'youchuu The Animation or In'youchuu Etsu and appreciated how those blend genre framing with adult content, this scratches a similar itch. It's short, weird, and leans hard into the sci-fi framing rather than abandoning it halfway through. Don't go in expecting deep storytelling — go in expecting a strange little OVA that takes its own ridiculous concept seriously enough to make it work on its own terms.