[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/alien-nine-episode-3-3.jpg]]
[[caption-width-right:350:Keeping E.S. #9 safe from {{Alien Invasion}}s: left to right, Kasumi, Kumi and Yuri.]]

'''''Alien Nine''''' is a science fiction manga and OVA about a trio of 6th grade girls (Yuri Otani, Kasumi Tomine, and Kumi Kawamura) who are selected by their elementary school to become alien hunters. Donning special uniforms, with rollerblades and helmet-like creatures called Borgs that they wear on their heads, the girls are tasked with hunting down and capturing the marauding aliens that periodically threaten their school. What starts off as a straightforward cute action story turns disturbing rather quickly when one of them gets ''eaten'' by an alien and suspicions about the teacher running the program and the principal arise.

''Alien Nine'' consists of:
* The original three-volume manga that ran from 1998-1999.
* An OVA released in 2001 that became a cult-classic.
* A one-volume sequel manga released in 2003, ''Alien 9: Emulators''.

Now has its own Character Page. Contributions are greatly encouraged and appreciated.

Compare ''Anime/PuellaMagiMadokaMagica''.

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!!Tropes:

* AdultsAreUseless: [[DeconstructedTrope Deconstructed]]. The school administrators eagerly send pre-teen girls out to capture aggressive aliens, and their parents only wave them off and tell them to continue doing their duty. Cue heavy physical and psychological trauma to the girls and regretful parents. [[spoiler:[[JustifiedTrope Justified]] in the case of the school administrators: ''Emulators'' reveals it's all part of a {{Masquerade}}]].
* AlienBlood: It's dark green.
* AlienInvasion
* AllThereInTheManual: The OVA was only four episodes long, cutting off just as things were getting interesting. The manga, however, continues the story...
* AnimatedAdaptation
* AssimilationPlot: The various alien species appear to have this in mind for humanity [[spoiler: and manage to succeed with Kasumi and Kumi, and have already succeeded with their teacher]].
* BarbieDollAnatomy: In the OVA.
* BattleInTheCenterOfTheMind: The climax of volume 3. [[spoiler:Even after the Sunflower is physically removed from her head, Yuri still has to fight to get it out of her mind]].
* BioPunk
* BizarreAlienBiology
* BodyHorror: When Kumi [[spoiler:becomes a borg]].
* BreakTheCutie: This series makes pushing all three girls to their mental/emotional/physical limits an art form. By the end, two of the three are broken: whether they seem that way or not: and the third a candidate for a Post Traumatic Stress Disorder diagnosis.
* BrotherSisterIncest: The OVA implies that Kasumi and her big brother had this type of relationship. At the very least, Kasumi had a quiet obsession for her brother. Whether it was one-sided or not is open for debate.
* CloudCuckoolander: Kasumi seems a bit like this... until we find out about her [[DarkAndTroubledPast past]].
* ConspicuousCG: The drills. Not shabby for 2001, though.
* CosmicDeadline: The last volume of the manga has about as much plot as the previous three.
* DarkAndTroubledPast: Kasumi and Kumi have them.
* EarnYourHappyEnding: After four volumes of trauma, ''Emulators'' ends on a relatively happy note.
* TheEndOfTheBeginning: PlayedStraight and [[LampshadedTrope Lampshaded]] by the OVA's last episode, it also being the title of said episode. It hints at [[spoiler:an interstellar conspiracy, with the heads of the Alien Party committees in each school and their principals in on it]]. Of course, you have to read the [[AllThereInTheManual manga]] to see all this.
* TheEndOrIsIt: At the end of the original manga, [[spoiler: Yuri makes it out, still an unfused, '''ordinary''' human. ...And then she notices in the mirror that a lock of her hair has become curly]]. ''Emulators'' reveals that [[spoiler: that single drill is the extent of Yuri's transformation and she's still human. There's still the matter with the Yellow Knives, though]].
* FragileFlower: Yuri. Just ''looking'' at her is enough to start the waterworks!
* {{Gorn}}: The [=OVA=] is not afraid to show aliens getting bloodily maimed. The manga goes further, with the girls getting maimed themselves.
* HeelFaceRevolvingDoor: [[spoiler:Kasumi tries to kill Kumi]] during the Yellow Knife incident, is brought back to semi-normal after [[spoiler:becoming one]], kills [[spoiler:Megumi's borg]] which allows her Yellow Knife spawn to eat and possibly kill the rest of the school, and tries to force Yuri into [[spoiler:fusing with Kumi]] without regard for the former's life in an [[WellIntentionedExtremist attempt to save Kumi]] in ''Emulators''. However, it is implied that the Yellow Knife is manipulating her throughout it all.
* IKnowYoureInThereSomewhereFight: [[spoiler:This happens after Yuri becomes host to a Sunflower]].
* ImprobableAge: Even lampshaded by one of the characters.
--> '''Monami''': Objection! We're kids. That's an adult job.
* JapaneseRanguage: In the OVA, the girls' profiles show their "[[PersonalityBloodTypes brood types]]" as AB.
* LovecraftLite: [[NightmareFuel Well, maybe "lite" isn't exactly the right word]].
* {{Masquerade}}: Ms Hisakawa is actually releasing most of the aliens they're supposed to capture [[spoiler: because the real objective is to turn the girls into drill clan symbiotes like herself]].
* MindRape: Several types of symbiotes are capable of this, including Yellow Knives and Sunflowers.
* MindScrew: The dream sequences.
* PhallicWeapon: The gladius aliens use drills to ''penetrate'' things. They also look like penis heads, and their name is Latin for "sword".
* PowerTrio: Yuri, Kumi, and Kasumi.
* PrehensileHair: That forms into ''auger bits'', no less. In ''Emulators'' there's a fourth alien fighter whose hair hasn't settled down and moves around on its own.
* RapeAsDrama: The OVA implies [[spoiler: Kumi]] took advantage of the Yellow Knife's disabling field and at least molested [[spoiler:Yuri]] in the locker room.
* RollerbladeGood
* SixthRanger: Monami (although she's actually a Fourth Ranger).
* SoundtrackDissonance: The OVA likes to play "cheery" music inappropriately. Most notable is the middle of episode 3, when bubbly opening theme song playing while the girls fight a giant "centipede" while Yuri loses it.
* SplitPersonality: [[spoiler:Kasumi]], after being eaten.
* StarfishAliens
* SugarAndIcePersonality: Kumi is a Type 1.
* ThisIsADrill: Choice of weapon of the borg and gladius aliens.
* TwentyMinutesIntoTheFuture
* {{Yandere}}: Kumi becomes an obsessive type over Yuri after [[spoiler:Kumi fuses with her borg]].
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