[[caption-width-right:200:From left to right: Sou, Mashiro, Kureha.]]

''After School Nightmare'' (''Houkago Hokenshitsu'', literally translated as ''After School Infirmary'') is a {{shoujo}} PsychologicalHorror {{manga}} written and drawn by Creator/SetonaMizushiro. It is about a [[{{Hermaphrodite}} biologically intersex]] teenager, Mashiro Ichijo, whose body is male from the waist up but female from the waist down. Mashiro was raised as a boy but is terribly afraid that his various weaknesses and failings mean that he is actually a girl.

The manga begins with young Mashiro getting his first menstrual period. He comes across a strange woman, the clinician at a school clinic that he never noticed before, who tells him he must attend a special class once a week if he wishes to 'graduate'. In this class he and other troubled teens enter a DreamWorld, where they take on the form of their "true selves" and must fight for the right to "graduate". Mashiro also finds himself in a LoveTriangle with Kureha, a pretty girl who [[DoesNotLikeMen fears men]] and likes him because he is not quite male, and Sou, a handsome boy who [[StupidSexyFlanders believes that Mashiro is a girl]].

Angst, drama and Freudian imagery ensue...

!!''After School Nightmare'' provides examples of:

* AbusiveParents: Kureha's father.
* BastardBoyfriend: Sou.
* BittersweetEnding: [[spoiler:In "the real world," a fire breaks out in the hospital where the lead characters' mothers are staying, and every one of the main characters dies, never having a chance to be born, except for Mashiro, who comes into the world as a female. However, Real-World!Mashiro meets a Real-World!Sou in the final few pages, which makes it a ''little'' bit sweeter in the end.]]
* BlackKnight: [[spoiler: Kurosaki]]'s form in the dream world, who acts relentlessly against Mashiro.
* BrokenBird: Kureha, who was [[spoiler: [[RapeAsDrama raped as a child]], now has a deep [[DoesNotLikeMen fear of men]] and has a mild FreakOut whenever a guy gets physically too close to her]].
* BrotherSisterIncest: Between Sou and [[spoiler:Ai]]. Except that [[spoiler:the version of Ai that Sou had his "first time" with was the ImaginaryFriend version of her, and he actually hasn't had any relations of any kind with his real sister in a while.]]
* DamselInDistress: Kureha, which especially shows in the dreamworld due to the form she takes. She heavily relies on Mashiro to protect her there. Until she gets her CharacterDevelopment.
* DoesNotLikeMen: Kureha, but it's understable since she [[spoiler: was [[RapeAsDrama raped as a child]] and [[AbusiveParents her father was an abusive bastard]].]]
* DoesThisRemindYouOfAnything: [[spoiler:When Kurosaki reaches into Mashiro's wound (the final time) and roots around in there to find the key. Mashiro's [[ImmodestOrgasm moaning]] pretty much sealed the deal.]]
* DreamWorld: This is one of the main settings of the story. It can be entered by falling asleep in the infirmary.
* DreamWithinADream: Chapter 36.
* ElegantGothicLolita: Ai as a child, and in the dream world.
* TheEndingChangesEverything: [[spoiler:As it turns out, the entire story symbolises the birth of a pair of twins. The female twin is the now female-identifying Mashiro, while her twin brother died during childbirth.]]
* FirstLawOfGenderBending
* GirlishPigtails: Kureha, complete with [[HairDecorations hair ribbons]], and Midori with her twin braids.
* {{Hermaphrodite}}: Mashiro.
* ImaginaryFriend: [[spoiler: The more commonly seen version of Ai.]]
* JeanneDArchetype: [[spoiler:Kureha's form in the dreamworld after her character development.]]
* KendoTeamCaptain: Kurosaki
* {{Kuudere}}: Sou, who is generally stoic and aloof most of the time; however, he tends to be more affectionate with Mashiro after falling in love with him.
* MagicalRealism
* TheMatchmaker: Mashiro tries to help Shinbashi so he can befriend his crush Kureha, but it doesn't work. Later, [[spoiler: Shinbashi helps both Mashiro and Kureha with their relationship]]
* MeaningfulName: Setona Mizushiro often uses kanji for colours in many of the characters' family names as subtle hints to their personalities and identities.
* MindScrew: The ending. [[spoiler:The main setting of the story is a sort of symbolism towards what is happening in the real world - namely, everyone dies in a hospital fire, except for Mashiro, who is born as a female.]]
* NightmareDreams: And '''how'''!
* NoPeriodsPeriod: Averted on the very first page of the manga, to Mashiro's horror. Mashiro plays it off as "an illness which makes me bleed once a month."
* OutfitRipSexCheck: In the DreamWorld, a character tries to figure out Mashiro's gender by ripping open his uniform with a sword.
* PrinceCharming: A [[DeconstructedTrope Deconstruction]] of this character trope. Mashiro idealizes what it means to be a man and uses that prince archetype to model himself after. Most of the girls he interacts with later on in the manga begin calling him out for assuming that every girl needs to or even wants to be helped or saved. In fact, many of Mashiro's princely acts frequently get him killed in the dream world because he assumes that the girls around him are fragile and need a man to rely on. It is that very thinking that keeps Mashiro from even considering becoming a girl because in his mind men are strong and women are weak.
* RapeAsDrama: [[spoiler:Kureha was raped as a small child. This, along with her [[AbusiveParents abusive father,]] is what shapes her [[DoesNotLikeMen fear and dislike towards men.]]]]
* RunningGag: Try to count how many times Sou gets slapped by various people. Occasionally justified.
* StalkerWithACrush: Sou.
* StepfordSmiler: Kurosaki.
* TheirFirstTime:
** [[spoiler:Ai confesses Sou's was with her. Of course this can't be true because this version of Ai is actually Sou's ImaginaryFriend.]]
** [[spoiler:After Mashiro chooses to be a female, he has troubles to act and identify himself as a girl. After realizing he's in love with Sou, he asks him to "make him feel like a woman".]] Cue their first time in the gym's storehouse.