Keraku-No-Oh: King of Pleasure

Keraku No-Oh: King of Pleasure is a 3 part Hentai OVA made by Five Way. It was made in 2002.

Bullied all his life, Ryouichi has given up on life due to brain damage he suffered as a child. When his childhood friend, Chihiro Himenoki feels guilty for causing it, he asks for sex in return. Discovering he is infallible at sex, he decides to get revenge on the girls who bullied and belittled him with his newfound confidence and sexual endurance. Chihiro ends up being his unwilling accomplice out of both guilt and desire.

Tropes used in Keraku-No-Oh: King of Pleasure include:

All Amazons Want Hercules: Kanata actually wants to pinned down by a man stronger than her and masturbates at the thought of it. She even has rape fantasies. She gets her wish by being gangraped by the Judo team she was captain of.
Amazonian Beauty: Kanata is pretty strong.
Asshole Victim: A lot of Ryouichi's rape victims were this. His first victim, Kaya, was the leader of a gang of bullies that was trying to kill him and Miyaka was such a sadist, even Chihiro was happy to see Ryouichi get her.
BDSM: Ryouichi does this with Chihiro for "talking back to him." Also does to to Tamana for his amusement.
Be Careful What You Wish For: Kanata, when you have rape fantasies, this is the only outcome.
Berserk Button: Calling Ryouichi filthy sets him off when he discovers how good he is at sex. Nagawa's head got slammed when she did.
Bigger Is Better in Bed: Chichiro claims Ryouichi's penis was the biggest she'd ever seen. It's also one of the factors in Ryouichi being the King of Pleasure.
Big Man on Campus: Ryouichi becomes this at the end when his revenge is complete. He gives it up to be with Chihiro in America.
Bittersweet Ending: Ryouichi gets his revenge and goes to America to be Chihiro. But he believes sex is merely a game and seeks to find more girls to have sex with. It ends with Chihiro hoping he one day understands love while having sex in the plane.
Blackmail: How Ryouichi gets two of his victims to have sex with him.
Brother-Sister Incest: Technically brother-in-law, but this happened to Tamana when she lost her virginity by rape. Even Ryouichi was disgusted.
Bully Hunter: Ryouichi targets female bullies.
Buxom Is Better: Pretty much every girl in the series is this.
Chick Magnet: Ryouichi becomes this at the end of the series.
Childhood Friends: Ryouichi and Chihiro.
Covert Pervert: Several of Ryouichi's targets are this. Once Ryouichi finds out, he uses that to his advantage.
Disproportionate Retribution: While most of Ryouichi's victims were horrible people, the final target, Tamana Tsukino's only crime was giving him disgusted looks. Turns out her nose is highly sensitive and Ryouichi's "unique fragrance" was secretly turning her on.
Even Evil Has Standards: Despite all the bullies trying to kill Ryouichi, Kara was so brutal even they felt uncomfortable watching it.
- Ryouichi is only out for revenge on the girls that wronged him or if he has something to gain from it. Otherwise, he'll leave you alone.
- Even Ryouichi seemed disgusted by Miyako's sadism towards other students. He also seems disgusted with pedophilia when Tamana tells him how she lost her virginity.
For Want of a Nail: See Pity Sex below.
Freudian Excuse: Ryouichi's brain damage and constantly being bullied set him off on his path of vengeance when he discovered he is infallible in bed.
Girl-On-Girl Is Hot: Ryouichi makes Nagawa and Chihiro have sex for his amusement.
He Who Fights Monsters: Ryouichi's desire for revenge turns him into a rapist.
Hunk: Ryouichi is quite buff likely so so he could survive being bullied. The change in animation slims him down though he's still quite buff at times.
If It's You, It's Okay: Nagawa, the teacher, is a lesbian and even she joins Ryouichi's harem, thus making him an exception.
It's All My Fault: Chihiro blames herself for what happened to Ryouichi when they were children. This along with Ryouichi being the King of Pleasure, makes her an unwilling accomplice.
"It's Not Rape If You Enjoyed It": All the girls Ryouichi rape end up being willing members of his harem. One of them is his lesbian teacher.
- This is also how Tamana developed her sperm fetish when she was raped by her brother-in-law.
Jerk Jock: Kanata, captain of the judo team, was one of the bullies that picked on Ryouichi. It makes her one of his targets.
Ladykiller in Love: Even after gaining a harem and doing better at school, Ryouichi ends up feeling lonely for Chihiro and decides to move to America to be with her. He's still too young to fully understand love though but Chihiro hopes one day he will.
Loners Are Freaks: Ryouichi so much so that not only is he heavily bullied to the point where people were trying to kill him, even his own parents have little respect for him and tell his younger brother not to be like him.
Ms. Fanservice: Take your pick of any of the girls.
No Sympathy: During a flashback, the nurse, Miyako, told Ryouichi to just go home and throw a filthy thermometer in the disinfectant while he was suffering a bad fever without any hint of compassion. She's also a sadist.
Pity Sex: Chihiro has sex with Ryouichi when she feels guilty for the brain damage she caused him when they were children. It's how Ryouichi discovers how good he is at sex and starts his quest for revenge.
Plot With Porn: The story of a bullied loner who discovers his sexual prowess and begins a quest for revenge.
Puppy Love: Ryouichi and Chihiro when they were children. Chihiro desperately wants to go back to that.
Rage Breaking Point: Chihiro puts up with Ryouichi's desire for revenge hoping it would bring back the boy she fell in love with. When he decided to get "revenge" on Tamana, she finally has enough and slaps him because he has no real need to take revenge on her. She then runs off begging for the kind boy he used to be.
Revenge: Ryouichi's entire motive. He succeeds at the end.
Rich Bitch: Kaya, the leader of the bullies is supposedly quite wealthy according to Ryouichi.
Sex God: With his very big penis, limitless stamina, and extremely quick recovery rate, Ryouichi is the titular "King of Pleasure." This along with Chihiro feeling guilty for the accident that gave him brain damage keeps her under his control and turns his female tormenters into his harem.
Sex Slave: Chihiro becomes this due to feeling guilty for the accident that made Ryouichi suffer. She ends up being this willingly after Ryouichi gets his revenge and he goes to America to be with her.
Smarter Than You Look: Ryouichi, despite having brain damage is quite clever and able to set up traps for his victims or blackmail them into sex. Ryouichi even sets up Kanata to be gang raped by the judo team to wear her down so she wouldn't be able fight back when he raped her himself knowing how capable she was as a fighter.
Tragic Villain: Ryouichi ever since he got brain damage ended up bullied all his life. Once he discovers how great he is at sex, he decides to get revenge.
Used to Be a Sweet Kid: Ryouichi until his brain damage ruined his life. Chihiro wants Ryouichi to go back to that. The ending hints that one day, he will.
Would Hit a Girl: Ryouichi injures Nagawa when she called his penis filthy.