Your Magical Name is Rina Witch

Mind-consuming creatures called Eaters have crept across the world so slowly that humanity's only real defense has become witches — and witches need mana. That's where Toshiya comes in. He gets paired with a witch-in-training named Rina at a school specifically designed to produce that mana through, well, intimate partnerships between students. It's essentially a magical girl setup where the power source is exactly what you'd expect from a hentai OVA. Don't let the fantasy framing fool you into thinking this is subtle about what it is. It's one episode, based on a visual novel from T-Rex, and it leans fully into the premise without much hesitation. What actually works here is that the setup is more thought-out than most entries in the genre — there's a genuine world with stakes, a threat that matters, and a dynamic between Toshiya and Rina that has some actual tension to it before things escalate. If you've seen something like Mahou Shoujo Ai or Discipline: The Record of a Crusade, you'll recognize the structure: fantasy or school setting, paired characters, adult content that's more connected to the story than it usually is in this genre. It's a single OVA, so it doesn't overstay its welcome. If you're looking for a hentai that at least bothered to build a coherent world around its content, this one delivers on that front reasonably well.