Makai Tenshi Djibril

Plot
At the beginning of summer break, Naoto Jinno asked Rika Manabe to go out with him and was trying to propose his love to her at a park and eventually make love. They were then interrupted by a strange little boy dressed in medievil costume. He declared himself that he was a private in the army of Hell and was known as "the great Asmodeus”. Asmodeus dispatched tentacle creatures to knock Naoto down and grab Rika in an attempt to kidnap her, saying that he will corrupt her soul. At that very moment, a girl named Luvriel came to saved them after battling Asumo. Luvriel was knocked unconscious in the battle and was taken to Naoto’s home by them.

After regaining consciousness, Luvriel told them that the angels knew that the demons were suspicious and she was sent to the human world to investigate. She said that she was following the scent of the devil which lead her to the scene. Luvriel and Asmodeus lost most of their powers from that fight. So she needed someone else to become an angel to fight in her place and only Rika can do it because only a girl can become an angel. So Rika cheerfully volunteered to be an angel. However, they both were discomfited to learn that in order for her to become an angel, there are two conditions for that. She has to wear Luvriel's halo and store Amore power by making love with someone she cared for. Naoto was the only one to do that job, so they both reluctantly agreed to make love together.

After the fight, Asmodeus found Meimi Otonashi. He happened to see her stagger away crying after spying on Naoto as he asked Rika to go out with him. Taking advantage of her jealousy for his prey, Asmodeus turned Meimi into a demon and named her Misty Mei to help him attack and capture Rika. (But, much to Asmo's dismay, she turned out to be an uncontrollably temperamental subordinate [she really put the mental in temperamental] and thought of him as her slave.) Meanwhile, Luvriel had Naoto and Rika have sex together so that Rika could turn into "St. Djibril" (Jiburiru) to help her fight against Asmodeus.

After Luvriel tells them of some of the different sex techniques that they would have to engage in for Rika to gain different battle powers Rika becomes frightened of doing it all and runs out of the house and finds Asumo and Misty Mei attacking people in the park. (All of their attacks are by sexual assault with tentacle creatures.) Naoto and Luvriel catch up with her and Naoto throws Luvriel's halo to Rika’s head and she turned into Djibril. While her first defensive attack doesn't go well for her, Misty Mei literally blows (up) the attack anyway with her jealousy.

In the next three volumes it's try, try and try again for Asumo and Misty Mei as Naoto keeps not-so-selflessly "helping" Rika store-up Amore power with their "special training" and in the third volume Asumo's superior, General Reirouge tries to help him before his next attack by weakening Naoto by seducing him, while disguised as another character, in his home. But Asmo and Misty Mei wind up attacking Rika in another room while Reirouge is trying to wear Naoto out and she is no match for his sexual prowess and is unable to hold onto him when he takes off to help Rika after hearing her screams for help. In the last volume Reirouge takes matters into her own hands leading the next attack and takes Djibril to a special chamber she created for a demonic ceremony to turn Rika into a demon- angel (but she spares Rika from despair by not telling her why). Does Reirouge succeed with her plan?

After the first series ends, the story continues with "Djibril, the Second Coming" ("Book"s 1-4). New characters including Hikari Jinno (Jinno Hikari), Naoto's little sister (later on he calls her his sister-in-law and still later she becomes his step sister), who returned from studying overseas for a reason she keeps a secret and the new demon Miss Rococo, Asmo's sister (that is not mentioned in the anime movie), who seems to be a lesbian, appear in the new series, but Asmodeus and General Reirouge do not. Within the series, Rococo captures Meimi Otonashi with her tentacle creature the "Eternal (and frequently internal) Worm” and separates Misty Mei from her with the worm’s “special fluids” and Misty Mei attacks and captures Rika with Rococo's Eternal Worm.

After the kidnapping, Naoto becomes upset that Rika was taken away. Similar to Rika's fate in the first series, Luvriel gets Hikari to become a Djibril. However, for this to occur, Naoto must have sex with his step sister. Initially, Naoto is shocked and angered at Luvriel for insisting on such an incestuous-like act and refuses, but soon changes his mind when Hikari offers herself to him in order to save Rika. (Hikari has returned from overseas to confess her love for Naoto anyway.) After they have sex, Luvriel transforms sister Hikari into Djibril Aries and fights the forces of evil... including Dark Djibril, who Rococo transformed Djibril into by forced sex with her Eternal Worm monster and herself- (including by transforming her clitoris into a penis. [In a later "book" episode she does the same to Djibril].) Does Djibril Aries defeat Misty Mei, Rococo and does Dark Djibril turn back into Rika?

In the next movie volumes (which are only available in Japanese and with Japanese mosaic style censorship), this peace is short-lived, with a strange new photography student taking pornographic pictures of some of the students, something connected to the return of Misty Mei. When a more powerful monster than they've ever faced before attacks them, Hikari Jinno is abducted, and a new angel in the form of a blue-haired virtual girl- in fact a computer program named Nagi (or N.A.G.I. - New Angelic Gaia Interface, who is renamed Nagi Jinno) is activated and sent (by falling into Naoto's bath- while he's in it)- to help. She apparently is only activated when the risk is too high for a normal angel or human battle-angel to be sent into the field. Once the major danger has passed, she is recruited to help with the main mission, after some kind of strange spell is being cast on Rika and Hikari. Can Nagi rescue Hikari... or is it too late already?