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Hiyama Ren is an apathetic first-year who, despite having been appointed student council chairman, ignores everything around him, including his own academic achievements. Then, one day, fellow classmate and student councilmember Takagi Yuka (who has an unrequited crush on him) requests his help and support with the upcoming cultural festival.

It seems that Yuka’s uncle, Kuonji Itsuki, is a nationally-renowned hypnotherapist, and Yuka thinks that a hypnosis show would be a big draw for the fair. Hiyama is interested, but wants proof that hypnosis works. So Yuka invites Kuonji to give a demonstration before a select audience, including Hiyama. After seeing proof of its effectiveness, Hiyama decides to use it to make the world a better place, no matter what…

Often (understandably) compared to ''Manga/DeathNote''. Both are {{Shonen}} {{manga}} which are constantly mistaken for {{Seinen}}[[note]] Manga/DeathNote was published in ShonenJump, LostBrain in Magazine/ShonenSunday[[/note]]. Both star bored, brilliant high schoolers who come across a supernatural power of some kind and decide to use it to make the world a Utopia. Both also end up playing XanatosSpeedChess against an opposing {{Chessmaster}} who is leading the effort to catch them.

Lots of hidden spoilers below.
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!!Tropes seen in ''LostBrain'' include:
* ArchEnemy: Hiyama and Kuonji, after Kuonji publicly decries the Third Party’s actions.
* BadassNormal: Hiyama and Kuonji. After all, anyone can learn hypnosis…
* [[spoiler: BetterToDieThanBeKilled: Hiyama opts to make a suicidal escape attempt rather than be caught by Kuonji and the authorities.]]
--->[[spoiler: '''Hiyama''': Just as you all deny my world, I deny the existence of your world. I have no intention of being judged by the likes of you!]]
* BeautifulAllAlong: Sonoyama Mizuki, [[spoiler: after Hiyama gives her a hypnotic self-image makeover.]]
* {{Bishounen}}: Hiyama and Kuonji, although Kuonji is more androgynous.
* {{Brainwashed}}: It would be easier to list the people Hiyama ''doesn’t'' hypnotize, either directly [[spoiler: or through Kanbara Hayato]].
* BrainwashedAndCrazy: Ōsawa, after Hiyama gets through with him.
* BunnyEarsLawyer: Despite his taste in fashion, Kuonji Itsuki is a talented hypnotherapist.
* CriminalMindGames: See DivideAndConquer below.
* DangerouslyGenreSavvy: Hiyama finds out that [[spoiler: Kuonji has escaped from jail, and learns where he is hiding.]] What does he do? Like any good citizen, [[spoiler: he anonymously phones the police, who promptly recapture Kuonji.]]
* DivideAndConquer: Hiyama manipulates events so that the police think [[spoiler: Kuonji is the Third Party.]]
* TheDragon: Shitara Haruhide, after he learns the reasoning behind Hiyama’s master plan.
* {{Expy}}: Hiyama is Light Yagami with white hair; both of their motivations and personality are extremely similar to the other. Even their houses have similar layouts.
* FakeMemories: Hiyama swaps out [[spoiler: Yuka’s]] visit to his house for a visit to the park.
* FakingTheDead: Though it is considered unknown the last pages in the final chapter shows a person who looks like Hiyama walk among a group of people and remain hidden.
* [[spoiler: GoneHorriblyRight / HoistByHisOwnPetard : Hiyama is (probably) killed because his hypnosis is ''too'' perfect and caused a DoubleThink LogicBomb.]]
* GreenLanternRing: Hypnosis. Justified, in that most, if not all, of the tricks pulled with hypnosis are entirely plausible.
* HeroAntagonist: Kuonji Itsuki.
* HiddenEyes: Hiyama, when he is being bullied in the first chapter.
* IdiotBall: It's odd how Kuonji never even suspects Hiyama of any wrong doing even when everything bad and odd happening around the school can in some way be linked to him.
* LaserGuidedAmnesia: Many of Hiyama’s “subjects”, but especially [[spoiler: Onoda-sensei, who Hiyama manipulates as part of his scheme to discredit Kuonji, and who suffers from temporary gaps in her memory as a result.]]
* LikableVillain: Hiyama’s motives are admirable, if not his methods.
* [[spoiler: LogicBomb / MindScrew: Hiyama accidentally creates one when he simultaneously "programs" his victims with both a strong will without weaknesses and absolute submission to him (a la [[Film/MontyPythonsLifeOfBrian "Yes! We are all individuals!"]] followed by a metaphorical YourHeadAsplode). The "bomb" goes off when Hiyama orders his thralls to kill Kounji, and one of them also happens to be holding a [[StuffBlowingUp detonator]]...]]
* MagicAIsMagicA: The real-life rules of hypnosis (i. e., what one can and can’t do) are usually followed by both Hiyama and Kuonji.
* ManchurianAgent: Ōsawa is Hiyama’s first experiment in this field. [[spoiler: Later, Hiyama manages to turn ''the entire student population'' into his agents by first putting them in a more…''receptive'' frame of mind.]]
* [[spoiler: MassHypnosis: Stage two of Hiyama’s plan hinges on using Kanbara to hypnotize most of Japan.]]
* MindControl: In spades.
* MindControlDevice: A mild use, in the form of [[spoiler: subliminal messages recorded in the background music played during Kanbara’s initial set of broadcasts.]]
* MindControlEyes: Mostly [[AvertedTrope averted]]. As in real life, people who are under hypnosis tend to have dilated pupils, not contracted ones.
* MindRape: What will happen to [[spoiler: Yuka]] if Kuonji probes too far into [[spoiler: her]] subconscious, according to Hiyama.
* MoreThanMindControl: [[spoiler: Sonoyama]] chooses to receive Hiyama’s hypnosis, knowing full well what his plans for [[spoiler: her]] are.
* [[spoiler: NeverFoundTheBody: Hiyama thought he could escape into a tunnel under the parliment(?) building, but it collapsed during the explosion so there's virtually no chance he survived. Than again, he was/is DangerouslyGenreSavvy...]]
* OrdinaryHighSchoolStudent: Most of the main cast.
* PowerTrio: Hiyama, Shitara, [[spoiler: and Sonoyama.]]
* PsychicAssistedSuicide: Although Hiyama isn’t technically psychic, the results are the same.
* RedShirt: If Hiyama introduces a “subject” to Shitara, chances are he’s planning to kill that person to further his plot. [[AvertedTrope Averted]] with [[spoiler: Sonoyama]], however.
* {{Shonen}}
* ShownTheirWork: Lost Brain demonstrates many real-world hypnosis methods, as well as describing the advantages and disadvantages of each method.
* SpellMyNameWithAnS: Is Kuonji’s given name “Itsuki” or “Ikki”?
* [[spoiler: SubliminalAdvertising: Part of Hiyama’s MassHypnosis plot involving Kanbara. It works.]]
* TeensAreMonsters: Hiyama gets accused of bullying a student, and is beat up when the teacher doesn’t believe the actual bullies. This is what later drives him to change the world.
** [[spoiler: In the epilogue, a bunch of teens complain that Hiyama didn't go all the way and destroy the world, which in Hiyama's defense was never his plan.]]
* ThatsWhatIWouldDo: How Kuonji initially comes close to defeating Hiyama without finding out his identity, [[spoiler: until Hiyama frames him for the murders.]]
* [[spoiler: TooDumbToLive: Hiyama makes a huge mistake when he doesn't realize that giving people a strong sense of self ''and'' absolute submission to him is an enormous LogicBomb -- and then he has them control an ''actual'' bomb.]]
* TriggerPhrase: Hiyama installs tons of triggers, [[spoiler: including having several victims commit [[PsychicAssistedSuicide suicide]] when Kuonji calls them.]]
* {{Ubermensch}}: Hiyama’s plans revolve around this.
* UnluckyChildhoodFriend: Ōsawa, while not considered a true ''friend'' by Hiyama, initially begs him to be friends with him since he lacks confidence on his own. Then Hiyama uses him as to [[spoiler: unwittingly assassinate the Secretary of State in a suicide bombing.]]
* UnwittingPawn: [[spoiler: Takagi Yuka]], repeatedly.
* UtopiaJustifiesTheMeans: Hiyama may not be as cocky as [[Manga/DeathNote Light]], but he does seem to be just as prone to sacrificing his pawns, [[spoiler: both figuratively and literally.]]
* VillainProtagonist: Hiyama.
* VisionaryVillain: Hiyama again.
* WellIntentionedExtremist: Hiyama, Shitara [[spoiler: and Sonoyama.]]
* WhenAllYouHaveIsAHammer: Hypnosis—both played straight and subverted, since hypnosis has many uses and forms, all of which (except past-life regression) are used by both Hiyama and Kuonji.
* WorthyOpponent: Hiyama knows better than to underestimate Kuonji’s doggedness and skill with hypnosis.
* XanatosSpeedChess: Hiyama’s battles with Kuonji.
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