Mouryou no Nie is a two episode OVA. The first episode aired in the later part of 2012 and the second episode in early 2013. One episode is 24 minutes long. It takes its source from a novel with the same name. The novel is only one volume and was published in 2011.
Hundreds of years ago, a big war between humans and monsters happened. Humans somehow won the war and sealed up the monsters deep in the mountains. Hayato, Chihiro, and Suzuna work hard to eliminate and seal up evil monsters every day. They are actually monsters, but they just want to coexist with humans. One day, they hear that the monsters sealed up hundreds of years ago are about to come out. To stop it, they decide to visit the place.
What the fuck did I just watch? Monster rape, tentacles, forced impregnation, mind break and monster birthing. There are two girls and the episodes revolve around each getting raped and bred respectively. Mouryou no Nie has some weird shit. Episode one is getting gang-banged by a bunch of frog dudes with tentacle dicks that lay a ton of eggs inside her. Episode two involves a ghost or something. She is tricked into thinking the boy she likes is alive and is ends up being a demon who uses illusion magic to take on the boy’s form.
I cannot find the DVD or the visual novel it was based off of. It wasn’t that long ago it was released, so I’m not sure where you could find these. But this streaming service might have it.