-->Thousand night, Recurrence night, Reverie and Invite.\\
and...[[=7days=] Immortal] Unreal BLACK THINGS.\\
The deep darkness of the hollow night. New shells of incarnation alight.\\
One swing of a sword. Sinuous white snake. Savage fangs of the beast.\\
Tonight, the deepest night. Blessing for all who confronts...

''Under Night In-Birth'' is a UsefulNotes/{{H|ighDefinition}}D 2D FightingGame made by French Bread, the makers of ''Videogame/MeltyBlood''. ''Under Night'' appears to be the SpiritualSuccessor of the ''Melty Blood'' series, as the game was originally developed as an HD port of the latter. The game even features Sion Eltnam Atlasia as a guest character under the name "Eltnum".

Under Night In-Birth takes place in a fictional modern-day setting some time in the 21st century. A phenomenon called the Hollow Night (虚ろの夜 utsuro no yoru) has been enveloping particular regions of Japan once a month for several centuries. Each area engulfed in the Hollow Night is beset by shadow-like creatures called Voids (虚無 kyomu) that utilize and feed upon a power known as "Existence", or EXS (イグジス igujisu). Normal humans cannot see or come into contact with Voids, but certain people have the potential to perceive them. Those who acquire this perception are targeted by Voids and risk either being consumed by them or losing their sanity. Under special circumstances, a person who maintains their sanity after being attacked by a Void can become a being known as an In-Birth (インヴァース invāsu). While this status places a person into a sort of limbo where they are neither living nor dead, they also gain the ability to control Existence. [[TheHero Hyde]], is one character who survived a Void attack and became an In-Birth.

Many characters are involved with the Hollow Night phenomenon, and several of them are affiliated with particular organizations. Two rival groups, Night Blade; (夜刀) and Licht Kreis, both serve to maintain order in areas affected by the Hollow Night but differ in their methods. The tarnished Night Blade; primarily hunt Voids, while Licht Kreis uses its lawful order and hierarchy to protect civilians. A third organization, Amnesia, is more chaotically structured and seeks to stop the influence of both Night Blade; and Licht Kreis.

Originally released on September 20, 2012 in arcades. It later received two major updates titled ''Under Night In-Birth Exe:Late'', released on September 9th 2013, and ''Under Night In-Birth Exe:Late[st]'', released on July 23, 2015. Both revisions served to rebalance the roster, updated graphics, and added several new characters, which can be read about on the game's character sheet. A UsefulNotes/PlayStation3 port of "Exe:Late" was released on July 24, 2014, and [[http://shoryuken.com/2014/07/04/aksys-games-bringing-under-night-in-birth-exelate-to-north-america-in-2015/ would eventually be localized in 2015]] in North Amercia, with Europe getting the game a few days later. It was later released, in it's Exe:Late form, on Steam on June 12, 2016. "Exe:Late[st]" is also receiving a console port planned on being released on UsefulNotes/Playstation3, UsefulNotes/Playstation4, and UsefulNotes/PlaystationVita consoles, this version is due July 20, 2017. "Exe:Late[st]" has since been annouced for an English Localization on consoles and will be releasing sometime in Late 2017.

''Under Night'' also appears in the MassiveMultiplayerCrossover ''VideoGame/BlazBlueCrossTagBattle'', opposite ''Franchise/BlazBlue'', ''VideoGame/Persona4Arena'' and ''WebAnimation/{{RWBY}}''.

!!1st Clause. DIVIDE.
* AlwaysNight: Caused by the titular phenomenon.
* AmbidextrousSprite: Hilda provides an aversion where her dress and eye colors will show the correct one regardless of which way she is facing.
* BadassLongcoat: Gordeau's purple duster, and Seth's black trenchcoat.
* {{BFS}}: Yuzuriha and Hyde wield ''very'' long katanas. Likewise, Gordeau uses an ''[[UpToEleven even longer]]'' SinisterScythe, and Nanase wields a broadsword as long as she is tall
* BigBad: Hilda.
* {{Bishounen}}: Hyde and Seth.
* BloodKnight: Carmine
* BloodyMurder: Carmine is shown to fight by using his own blood.
* CastFromHitPoints Carmine is also shown to use attacks that drain from his HP, he can heal via a grab.
* CastingAShadow: Both Hyde and Seth. Gordeau also has a few darkness-like attacks.
* CoatCape: Yuzuriha, with a kimono.
* ComboBreaker: [[SuperMode Veil Off]]. Somewhat subverted in that it's not usable while getting hit, unlike other fighting games with combo breakers.
* ComebackMechanic: {{Inverted|Trope}}. [[StatusBuff Grind Vorpal]] gives whoever's got the better offense a 10% damage boost once every 15 seconds and can sacrifice this buff for a ''Franchise/BlazBlue''-like LagCancel, sometimes leading to an UnstableEquilibrium.
* CoolSword: Hyde, Orie and Yuzuriha have one.
* DarkIsNotEvil: Despite his appearance, attitude, and job as an Assassin, Seth is the game's AntiHero.
* EldritchAbomination: Voids can drive people who can see them insane, causing them to become Voids as well. Those who can see them and maintain their mental stability become super-powered In-Births.
* FashionableAsymmetry: Seth and Hilda.
* GenkiGirl: Yuzuriha, if the music notes that come out of her sprite during battle are any indication.
* GratuitousEnglish: Just like [[Videogame/MeltyBlood its predecessor]], if not worse.
** Gordeau is, aside from the name and menus, the most notable example. GURIIMU REEPAAH! MORTARU SURAIDO!
** Hyde goes for PunctuatedForEmphasis when doing his Vacant Shift special move: "FIRST! SECOND! THIRD!"
** Orie follows Hyde combined with CallingYourAttacks for her super named "REST! IN! PEACE!"
* GuestFighter:
** ''Videogame/MeltyBlood''[='=]s Sion Eltnam Atlasia? [[spoiler: Technically, Eltnum is (more or less) Sion Eltnam Atlasia in an AlternateUniverse. She is subject to the same events as in Melty Blood, with most of Sion Eltnam Atlasia's back-story (and a massive design change). It should be noted that Eltnum is said to be intruding on the events of [=UNiB=].]]
** Played far straighter with [[VideoGame/AkatsukiBlitzkampf Akatsuki.]]
* {{Homage}}:
** Because of her existence, there are a few things from Eltnum that pay Homage to her ten years as a combatant in ''Melty Blood'', with her theme being the biggest one, [[BootstrappedTheme which is a remix of Blood Drain, Melty Blood Actress Again's title theme]]. [[spoiler: There is also the small fact that Eltnum [[LeaningOnTheFourthWall lives on the Forth Wall]] in story mode, having fought for ten years... she sees herself as viewing how the "next generation" stacks to herself. As such, she views her relationships with other characters as something of a SempaiKohai relationship, especially with Hyde. [[{{Cloudcuckoolander}} Just about everyone brushes her off as insane]]]]. And [[spoiler: She is finally free of that Goddamn [[{{Franchise/Nasuverse}} Shroom]] (read one: Kinoko Nasu) in her ending.]]
** Well, he is here... so you can't just summon the [[VideoGame/AkatsukiBlitzkampf Blitz motor user]] without some references to his struggle. [[BootstrappedTheme The theme that accompanies Akatsuki isn't his own, similar to Eltnum]]. War Start -Again- is a remix of title theme to Akatsuki Blitzkampf.
* HumanoidAbomination: Merkava. Most of the other Void probably qualify as well.
* IaijutsuPractitioner: Yuzuriha. With a {{BFS}} no less.
* KatanasAreJustBetter: Yuzuriha's got one nice katana. Hyde's sword is also a katana.
%%* KnifeNut: Seth
* LadyOfWar: Orie is pretty much checking every list of requirements of this trope. Yuzuriha's fighting style is also pretty graceful, but she's more [[GenkiGirl energetic]] than most examples.
%%* MightyGlacier: Waldstein
* MultiColouredHair: Both Hyde and Seth. Hyde's is black and blond, while Seth's is black and white.
* LightEmUp: Orie
* NoblewomansLaugh: Hilda, of course.
* OneHandedZweihander: How Gordeau wields his SinisterScythe.
%% * OneHitKill: They are called "Infinite Words EXS" (Pronounced "Exist").
* PowerDyesYourHair: Carmine's hair starts out white, but turns red when he activates his powers.
* RatedMForManly: Gordeau certainly looks the part.
* RedOniBlueOni: Hyde and Seth respectively. There's also the blue-haired [[LadyOfWar Orie]] and the redhead [[GenkiGirl Yuzuriha]]. Carmine and Gordeau also exhibit this trope in the former's Arcade Story.
* TheRival: Seth to Hyde, not unlike Creator/ArcSystemWorks other RedOniBlueOni rivalries ([[GuiltyGear Sol & Ky]] and [[Franchise/BlazBlue Ragna & Jin]]). Gordeau and Chaos are a friendly variant on this. Both sets of rivals have themes that play when they fight.
* ShockAndAwe: Akatsuki's Blitz Motor gives him this special property. It does make him very hungry very quickly though.
* SinisterScythe: Gordeau has this... [[HyperspaceArsenal notice that he's pulling it out of thin air]]
* SuperMode: Veil Off. Gives a 10% damage boost and doubles as a ComboBreaker.
* TokenMiniMoe: Vatista, who is also an ElegantGothicLolita and a LittleMissBadass on top of that.
* WalkingShirtlessScene: Gordeau, who has a [[NoShirtLongJacket long jacket]] instead
* WordSaladTitle: The Japanese trend of [[RuleOfCool naming things weirdly because it sounds cool]] strikes with a VENGEANCE in this series. (Though you have to wonder if they meant ''Inverse'', which MakesJustAsMuchSenseInContext as the alternative, but at least it's a ''word''.)
* TheWorfEffect: In Orie's Arcade mode, [[spoiler:Merkava comes in out of nowhere after [[FinalBoss Hilda]] is defeated, and devours/kills her before fighting Orie himself.]]
* WrestlerInAllOfUs: Waldstein, and to some degree Merkava.
* YinYangBomb: Hilda
* ZettaiRyouiki: Linne and Orie. There's also Eltnum.
'''BREAK DOWN'''\\
[-Vanishment of Void-]