Energy Kyo-ka

A manga series by Tamatsuyada, who follows High-schooler Kyouka Shiraishi works part-time at a local brothel.  She starts off using sexual favors for her reluctant step-brother and her fellow students to do things like pay her phone bills, but after being busted by the student council president Reona, she's given the option to work at Reona's mother's brothel.

 From this point, her money fixation gradually shifts to her coming to terms with her feelings for her brother, trying to protect him from potential seductresses, and trying to protect the brothel from rival factions.

The manga is currently ongoing, and received two animated OVAs essentially featuring the first three "chapters" of the story.

Energy Kyo-ka!! contains examples of:

• Absurdly Youthful Mother: The owner of the brothel, Erina Houjou, is only 34 years old, and has already has an adult daughter.  Justified in that she started working at her deceased husband's brothel when she was 14, and got married to him just a year later after having sex with him repeatedly.  Assuming she had her daughter a year after marriage, this means she's a 34-year-old woman with an 18-year-old daughter, and was married when she was younger than her own daughter now is. 
• The Ace: Kyouka is this for the brothel - she's capable of making any man orgasm to the point of exhaustion, no matter how large he is or how much stamina he has.  The only person who may be more capable than her is Reona's mother Erina Houjou, though she doesn't have sex nearly as often as Kyouka due to running the brothel.  In her younger days, Erina actually won her husband's hand in marriage after showing she was the most sexually gifted of all the girls at the brothel to the master himself.  When Lily Tanaka attempts a takeover, she knocks out Erina first, which forces Kyouka to take on her men instead.  This implies that Erina would have also been able to sexually satsify Lily's goons if the were conscious to try.
• Beach Episode:Omata de Nukarete Okuchi de Gokugoku? Yuujou to Fukujuu no Semen Gourmet Match. It is set on a beach where Kyouka's group is challenged by Rachel to competition involving...extracting fluids from males.
• Brother-Sister Incest:
  • Kyouka has been madly in love with her step-brother since they first met as children, and regularly blows hm to extort money out of him even when he protests.  Eventually, she stops charging him, and when Reona attempts to take his virginity on his birthday, Kyouka finally admits her feelings for him and fucks his brains out.  Notably, she actually starts by kissing him passionately - something she doesn't usually bother doing to other boys.  And after their first time together, she tries to have sex with him everyday when she can easily have sex with any other guy.  During a situation where she's forced to fuck an entire busload of men to use their semen to power the bus, she imagines them all being her brother to work herself up and easily gets enough semen for the bus.
  • Soushuuhen "Gaisen Fukki Hen" . Sherry turns out to also be incestuous with her brother.
• Distracted by the Sexy: Soushuuhen "Gaisen Fukki Hen" . At least from Kyouka's point of view. The moment she sees men offering free sex in the fertility festival, she seems to forget her previous objective of stopping Sherry of having a baby from her brother. But she still manages to recover and challenge her to a sex contest before it's too late.
• Flashback: The manga flashes back to Erina as a 14-year-old when she tells Reona and Kyouka how she met her husband, and the chapter covers their first meeting, first sexual experience and their marriage.
• Hot Teacher: Erina becomes this when she seduces the principal of Kyouka's school into letting her teach Kyouka and Reona's class.  She then takes over the school and uses her influence to make everyone have sex, all the while trying to monopolize Kyouka's brother for herself by attempting to seduce him.
• Huge Guy, Tiny Girl: When Lily Tanaka attempts to take over the Houjou brothel, she brings two massive African American men with her - Bob and George.  Both tower over everyone around them, and Reona initially attempts to have sex with  Bob despite her tiny frame before collapsing from the size of his penis.  Even Kyouka, who is the curviest girl in the brothel with a much bigger chest and butt than Reona is made to look tiny next to Bob - his entire body is still in view when Kyouka is sitting on his crotch, she only reaches up to his lower waist when comparing their standing heights, and her massive rear doesn't even fully cover his crotch when he's behind her.  The challenge for Kyouka in this situation is sexually subduing a man who is much larger, in terms of both height and girth.
• Making Love In All The Wrong Places: Kyouka has a massive orgy at a public festival just to prove to her brother's foreign friend that she's the most suitable sexual partner for him.
• My Brother Is Off-Limits:Soushuuhen "Gaisen Fukki Hen" . Kyouka gets very envious when her brother appears with a female friend that does turn out to have a romantic interest on him.
• Love Potion: Played with.  When Kyouka has to make every man on a bus orgasm to use the semen to power the bus, she pictures her brother's head on all of them to force her arousal into overdrive and then ravenously fucks them them into submission.
• Playboy Bunny: Botsuraku shita Houjou-ke Donzoko Shoukan no Fukkatsu o Kake, Mama no Nuginugo Gokuraku Service. Kyouka's group dresses like that to advertise their new prostitution service.
• Proud Beauty: Kyouka knows how attractive she is, and regularly uses it to get money for her odds and ends.  She wears her school uniform with an unbuttoned shirt to show her massive cleavage, has her sweater wrapped around her waste and wears a miniskirt.  She gave her brother blowjobs knowing even if he protested he'd be too aroused to stop her, and shortly after the manga starts she seduces three boys in her school into giving her 15 creampies, then charges them severely.  During a festival when a foreign friend of her brother is trying to seduce him, Kyouka proudly declares herself the "sluttiest girl in all of Japan" and challenges the girl to an orgy competition.  Being the owners of a brothel, Erina and her daughter Reona also know how enticing their bodies can be and use them to further the family business.  When Erina, Reona and Kyouka all gangbang Kyouka's brother, Reona even says that having sex with the brothel's top 3 women at the same time like he is would usually be worth 10 million yen.
• Took A Level In Badass: When Kyouka has to plow Bob into backing off, she initially has trouble making him orgasm because of his massive girth.  She eventually powers through this problem and forces him fully inside her with high-speed pistons, making him orgasm more than Lily can do to George, despite Lily having 20 years more experience in having sex and also having prior experience sleeping with extremely well-endowed men like Bob and George.
• The Rival: Reona sees Kyouka as this, though she later admits to herself that Kyouka is by far the most sexually enticing girl the brothel's ever had since her mother.
• You Got Spunk: Kyouka is so excited to have sex with any and everyone at the brothel during her first visit that she gets swarmed by all the clients.  She's then on the receiving end of their spunk, and notes how much she enjoys herself.  When she finally has sex with her brother, she practically melts while praising how great he is when he actually gets into it and starts fucking her like he means it. This especially impresses her since she has a massive amount of sexual experience, regularly having sex with 3-5 men at the same time, yet her brother is able to make her orgasm like crazy while losing his virginity to her.