Eiken

Eiken (rhymes with "achin'--erm, taken") is an 18-volume manga series and two-episode OVA by Seiji Matsuyama, where a dorky kid named Densuke gets dropped into a school full of large-breasted girls vying for his attention...but he just wants the eyes of the "cutest girl in school", Chiharu. Hilarity and extremely suggestive hijinks ensue as Kirika Misono, a Hot Amazon / Jerkass / High School Hustler, shanghais both of them into her private fiefdom, the Eiken club, to serve as her Butt Monkeys. At least this means Densuke has an excuse to talk to Chiharu now...

Long story short, this could be simply Seiji Matsuyama testing how much he could get away with.

Eiken is most well known in the West for its OVA, although it's a loose adaptation that hardly covers the original manga at all.

=== The Eiken manga and OVA contain examples of: ===


 * Accidental Pervert: Densuke.
 * A Cup Angst: Yuriko. Even when she gets a bigger cup size in the anime she still suffers from this. Kyoko shows signs of this too.
 * Absurdly Powerful Student Council: They attempt to disband the Eiken club in a manga Story Arc.
 * Anime Hair: Never mind the boobs. How is Kirika's ridiculous hair even possible?
 * Hell, how is it not dirty?
 * All Women Are Lustful: Played straight Up to Eleven. Granted while not 'every' last female in the manga or anime is this, the ones that do personify it 'really' personify it. Kirika has no problem stripping, groping, seducing or just plain trying to get naked with Densuke. Yuriko's favourite past time is smashing the poor boys face with her unique interpretation of a Groin Attack, and thats just the tip of the veritable iceberg of women 'knowingly' using their sexuality against this boy
 * Author Appeal: par the course with mangas written by Seiji Matsuyama, you learn that almost a good portion of the cast are well endowed. In fact, Eiken is probably an example of Seiji Matsuyama actually showing some restraint and really is one of his tamest mangas to date.
 * Berserk Button: Under no circumstances should you mess with Kirika's friends. If she can break a solid wall, your skull isn't gonna hold up if she decides to fight you.
 * This goes double for Lin Grace. You can abuse and destroy whatever she makes and she won't bat an eyelash. But if Densuke made it for her, and you break it, you WILL APOLOGIZE TO HER. Those earrings are there for YOUR safety, not hers.
 * Lin's bodyguard Leon is DEVOTED to her. if he THINKS you did anything to Lin, he will use as many knives as it takes.
 * Beyond the Impossible. Does this even need to be mentioned? No one's breasts could ever be that big.
 * Big Breasts Big Deal: Chiharu is Type 1 (Embarrassed) with occasional lapses into Type 5 (Ignorant), Kirika is a Type 4 (Vain), and Komoe is fully Type 5.
 * Breast Expansion: A more natural case in that Chiharu is still growing.
 * Brother Sister Incest
 * Butt Monkey: Poor Densuke...
 * Charles Atlas Superpower: Lin Grace, Rai and Den.
 * Chinese Girl: Lin Grace.
 * Clingy Jealous Girl: Yuriko, Chiharu's sister who decides to try seducing Densuke away from her sister.
 * Covert Pervert: The Teacher.
 * Cute Shotaro Boy: Densuke; Kirika makes him fulfill the crossdressing aspect of the trope.
 * Determinator: Densuke is a failure in many ways -- but he'll go to amazing lengths for those he cares about.
 * Dojikko: The Teacher, Komoe, and Densuke.
 * Ecchi: No, really?
 * Elevator School: Zashono Academy -- it fills an entire island.
 * Elephant in The Living Room: Komoe's unusual breast size, especially for her age.
 * Erotic Eating: There's a school competition that requires girls to eat chocolate-covered bananas! The anime also makes Kirika do this in almost all of her scenes.
 * Everyone Calls Him Barkeep: The nameless Teacher/Professor.
 * Fan Service Pack: Chiharu's breasts gradually grow over the course of the manga, starting with an impressive "88 cm" bust to a whopping "100 cm" - and it's implied that they'll keep growing further, like her mother did. The anime OAV takes this to a more ridiculous level, compressing all that growth within the span of what may amount in-universe to a single week!
 * Funbag Airbag
 * Gadgeteer Genius: Kyoko.
 * Gag Boobs
 * Gainaxing:
 * This series puts Gainax to shame!
 * Gay Option: Mikito, Chiharu's crossdressing brother (who tried to seduce Densuke disguised as Chiharu, and actually became interested.)
 * Though this trope could be considered subverted in a way becasue Mikito looks almost exactly like his sister given some Fake Boobs and is so damn convincing that he needs to tell people he's Mikito to avoid confusion.
 * Genki Girl: You could easily compare Kirika as a bigger-breasted version of Haruhi Suzumiya in terms of personality and energy.
 * Guilty Pleasures: Kyoko loves shojo manga, but is intensely embarrassed over at least Densuke seeing her collection.
 * Hot for Student: It rapidly becomes clear that the Teacher has it bad for Densuke, especially in the arc where Densuke has to meet her parents while being The Beard for her. It gets taken even further in one plot where she goes on a date with him, gets drunk, ends up french-kissing him, and would have taken his virginity if Densuke wasn't so fixated on Chiharu.
 * Hotter and Sexier: The OVA takes the fanservice way over the top -- which is something, considering the manga.
 * Humongous Mecha: Kyoko builds these; Densuke gets to be a guinea pig.
 * I Am Spartacus: The climax of the student council arc, when it appears Chiharu will be forced to leave the school.
 * Imagine Spot: Densuke.
 * Jekyll and Hyde: Inverted -- In the manga, Hot Amazon Jerkass Kirika spontaneously changes into a Nice Girl around Densuke on occasion. He never figures out whether it's a Split Personality, if Kirika's tormenting him in a creative way, or if she's letting the mask slip.
 * Jerk With a Heart of Gold: Kirika in the manga.
 * Latex Perfection: That physically identical, "personality-flipped" twin sister of Chiharu in the manga? That's actually Mikito, Chiharu's brother.
 * Loser Guy: Densuke.
 * Marshmallow Hell
 * Moment Killer: Brought to you by The Power of Friendship.
 * Ms. Fanservice: Kirika.
 * NSFW: Obviously
 * Nice Girl: Chiharu. Genuinely likes Densuke and is the only one who try to seduce him.
 * Official Couple: Densuke and Chiharu.
 * The Ojou: Lin Grace
 * Pretty Freeloaders: The Eiken club, who essentially evolve into Densuke's Unwanted Harem as the manga progresses.
 * Princess Curls: Chou Ginten.
 * Rapunzel Hair: Kirika.
 * The Real Remington Steele: After several chapters where Densuke's forced to crossdress, his little sister makes a surprise visit to Zashono Academy...
 * Ironically, Densuke was designed to look good as a girl...
 * Romantic False Lead
 * Sensei-chan: The teacher.
 * Storming the Castle
 * Student Council President: Chou Ginten, a Knight Templar Big Bad for an arc from the manga. (She's technically the treasurer, but she's bullied the actual president into submission.)
 * Supporting Harem: The Eiken club basically turns into this for Densuke and Chiharu.
 * Those Two Guys: Densuke's friends Shimada and Todoroki.
 * Trickster Mentor: Kirika, in her own way, acts as Densuke's guardian angel in his pursuit of Chiharu.
 * Except for all those times she butt-slams him right when he's about to say something to Chiharu.
 * Thanks for The Mammary: A lot. It turns out to be the reason why Chiharu is infatuated with Densuke.
 * Tsundere: Kyoko, Kirika.
 * Two Timer Date
 * Unwanted Harem: Densuke has the uncanny ability to have almost every girl given more than two panels fall for him without even intending to do so. Yet he only has eyes for Chiharu. Subverted slightly since he doesn't exactly tell them to stay away when they show interest in him.
 * Wholesome Crossdresser: Mikito.