La Blue Girl

 is an erotic anime and manga series by Toshio Maeda. Like Maeda's other hentai series ("e.g.", "Urotsukidōji"), "La Blue Girl" features a large amount of tentacle rape. It departs somewhat from its predecessors, however, by lightening the atmosphere with humor, lightly parodying the "tentacle hentai" genre.
An immensely successful series, "La Blue Girl" has inspired, over the years, several OVA series for a total of 14 episodes, a comic book adaptation, three live action movies, some PC games and some art books.
Story.
The story involves various ninja clans in a constant state of war with one another. The female protagonist is Miko Mido, a young ninja-in-training and the next leader of the Miroku ninja clan. This clan has control over the Shikima, a perverted race of sex-hungry demons led by Miko's father, the Shikima Lord. However, when thieves steal the magic compact that grants the clan this power, Miko has to fight the Shikima, utilizing her "sexcraft" ninjutsu in order to save the world. The Shikima live in a parallel dimension called the Shikima Realm, and one must perform specific sexual rituals in order to travel there.
Original Video Animation (OVA).
"Injuu Gakuen La Blue Girl".
Injuu Gakuen La Blue Girl (four episodes, 1992–93) is an adaptation of the original manga. Miko Mido is a teenage girl who is to be the next leader of the ancestral Miroku ninja clan. But the Suzuka clan steals the treasured compact that symbolizes the truce between the Miroku and the Shikima, a race of perverted otherworldly demons, and soon Miko has to use the sexual techniques of the Miroku to survive the assaults of the demons and protect her sister. After learning the truth behind her heritage and the identity of her true parents, she embarks on a journey to become a real Miroku ninja and would have to fight an ex-mistress-turned-traitor of the Miroku clan. 
"Shin Injuu Gakuen".
Shin Injuu Gakuen (two episodes, 1993) adapts the end of the manga, and as such is a follow-up and the conclusion to Miko's adventures in the first series. This time the enemies are Fubuki Kai, a rogue ninja who wants to defeat Miko and claim the title of best ninja, and the cybernetized survivors of the Suzuka clan. 
"Lady Blue".
 a.k.a. "Lady Blue" (four episodes, 1994). Features an original story about two ghosts, Kyoshiro and Shanahime, harboring an old grudge against the Shikima and attacking several of Miko's friends, including her first love. 
"Lady Blue" is about Miko's first love. Miko meets a young man named Hidemasa outside her apartment building and falls in love at first sight. Just when Miko thinks she can finally live like a normal girl and enjoy being in love, a mysterious female phantom appears in her school, sucking the life out of Miko's pretty young schoolmates. Fubuki reports that something is very wrong in the Shikima realm. Miko's parents are being tortured by the sound of flutes playing and no one knows why.
Miko and Fubuki investigate and find out that there is actually a love story behind it all, for the flutes belonged to a betrothed couple (Kyoshiro and Shanahime) 400 years ago, but treachery got in the way, so their love was never realized. The flutes are now cursed and Miko's dream guy, Hidemasa, is kidnapped by the vengeful phantom of Shanahime in order to resurrect her Kyoshiro.
"La Blue Girl Returns".
 a.k.a. "La Blue Girl Returns" (four episodes, 2001) is an anime series that continues the adventures of Miko Mido. Another original story, this time about the legendary Shikima Brain, a place rumored to bring total power over the universe. It is coveted by the insectoid ninja clan of the Mahoroba and protected by a mysterious clan, who may have a relation with Miko's previous life.
The plot begins when a race of butterfly-like demons named the Mahoroba want to enslave Miko Mido and her sister to steal the seal case that controls the Shikima. Their ultimate goal is to conquer the Shikima Brain, a legendary place of the Shikima realm which is said to confer the power to rule the universe.
English titles (four episodes)
Censorship issues.
Censorship is practiced differently both in Japan and in the U.S. due to their different laws: Japanese law technically discourages showing of genital hair or explicit genitalia, while the United States is more concerned about forbidding the display of sexual acts involving people under 18. Hence, there are censoring mosaics in Japan and scene removals and different ages of characters in the U.S.
While not featuring the censoring mosaics of the original Japanese version, the U.S. release of "La Blue Girl" was edited during the initial VHS release and all scenes featuring Miko's companion Nin-Nin engaged in a sexual act were removed, probably to avoid the charge of hebephilia.
For similar reasons, the age of the heroine was also altered: initially stated to be a 16-year-old high-schooler in the original Japanese version, she is an 18-year-old college student in the U.S. version. The various U.S. DVD releases contain this edited version.
In the U.K., the British Board of Film Classification famously refused to give it the certificate, allowing the movie to be sold on video.