Injuu Gakuen La Blue Girl, for those who don't know, follows the story of the Miroku clan, a group of ninjas that control the Shikima, a race of perverted demons. The protagonist, Miko Mido, is forced into a conflict with the Shikima after a group of thieves steal the contract that gave the Miroku clan power over the Shikima. Miko Mido, using her "Sexcraft" ninjitsu, must fight against the Shikima in order to regain the magical contract, and save the world.
Aside from being the very first hentai i ever saw, La Blue Girl holds an iconic name in hentai thru it's popular use of tentacle rape, a common theme in the work of Toshio Maeda, the creator of the series. However, it offers almost a parodic view of the "Tentacle Hentai" genre by giving a lighter and more humorous view on it, unlike Maeda's previous works such as Urotsukidoji.
I would definitely consider this to be one of the top hentai ever, even if it is sometimes overexaggerated. So now what do you think? Post below!

