->''"I don't know why, I have no idea, but quite possibly the single most important thing in the history of the universe is that I get you sorted out right now."''
-->-- '''The Doctor''', ''Series/DoctorWho'', "Flesh and Stone"

''Sekaikei'' (''sekai'' meaning "world", and ''kei'' meaning "type") is a Japanese term that is not clearly defined, spread primarily through the Internet but with some professional interest (there've even been [[http://asian.la.psu.edu/mapping/EVENTS/Entries/2009/4/1_Entry_1.html academic lectures]]). The simple definition of a Sekaikei story is the existence of a close relationship between two people, which turns out to be the sole driving force of the events, up to and including having all other happenings in the world at large depending on said relationship's fate, whether metaphorically or literally. The term "World-type" is related to the character-centric perspective of the world that comes out of such a story.

It can go something like this:

#Starts with very normal regular life. Then the central character becomes aware of a profound danger to the world at large.
#Said character meets another character who is also aware of the incoming apocalypse and may strive to prevent it.
#A relationship forms. There may be little description of how exactly the fate of the couple is related to the troubles of the world at large, but it is clear that the relationship between characters, rather than what they are actually doing, is their primary leverage to define what happens to all their surroundings.
#In the climax of the story, the characters are forced to choose between settling things on either the micro-level of the relationship itself, or the macro-level of how it affects the world at large. Typically, [[SadisticChoice both are exclusive]].
#A BittersweetEnding generally follows. If the world is chosen, the conclusion often involves a HeroicSacrifice on the part of one or both of the StarCrossedLovers, or them being separated and unable to ever meet each other again. If the romance is chosen, we may have [[AdamAndEvePlot the couple being the only survivors of an apocalypse]]. TakingAThirdOption is, however, also a common subversion.

Of note is the fact that the concept is notoriously difficult to turn into trope terms, as it is fairly controversial amongst anime fans and quite frankly ill defined. Even the term itself is a little bit nuts: they have to write the word in different systems in the middle of the phrase. "Sekai" is written with katakana while "Kei" is written with a Chinese character. Some say this kind of spelling in itself metafictionally represents how everything else, including literary theory, is actually revolving around the couple at the heart of the plot.

Compare SaveThisPersonSaveTheWorld, in which the world hinges [[BarrierMaiden on the shoulders of one person]], and TheNeedsOfTheMany, when the SadisticChoice is between [[ApocalypseMaiden said person]] or the world.


* ''LightNovel/HaruhiSuzumiya'' has the titular character as [[spoiler:a RealityWarper who unknowingly controls the world]] and so everybody else around her has to keep her happy. Most of this falls upon the narrator, Kyon.
* ''Anime/NeonGenesisEvangelion'' is believed to be a prototype of this concept. The characters can be said to draw the strength to face any given Angel from a specific relationship with others; in the end, when Shinji briefly reaches RealityWarper status, the fate of the world is dependent not on any specific relationship of his, but rather on what he wishes to become of the world in which some people hurt him, while others encouraged him not to give up.
* ''Manga/{{Saikano}}'' deconstructs the living hell out of this setup. Chise is an ultimate weapon in a war and how she decides to fight (if at all) depends on her boyfriend, Shuuji.
* ''Anime/ThisUglyYetBeautifulWorld''
* ''KannazukiNoMiko'', with the twist that the relationship is between [[GirlsLove two such girls]].
* ''Anime/VoicesOfADistantStar''
* ''Manga/{{Chobits}}'': Chi has an ambiguous ability that has untold horrible effects and it hinges on Hideki deciding on whether or not he wants to romantically be with her.
* ''Manga/{{Clover}}'': Similarly, Suu has an ambiguous ability which could reshape the world in multiple ways, and it soon becomes clear that she doesn't need to be escorted by a highly-trained and augmented ex-soldier because she's a target (although she is) but because of a long-ago connection between them. The plot isn't really about getting her to her destination, but about how the journey will affect what happens when she reaches it.
* ''Anime/EarthMaidenArjuna''
* ''Manga/{{Change 123}}''
* ''Manhwa/ImmortalRegis''
* ''LightNovel/ShakuganNoShana''
* The ''Manga/GaRei'' manga toss the role of "boy" and "girl" like volleyballs, but eventually it's between Kagura and Yomi.
* ''VideoGame/{{Xenogears}}'' is probably the MostTriumphantExample of the trope in gaming. Bonus points for having not only the current conflict, but also much of the world's history resting on the shoulders of the lead couple's ReincarnationRomance.
* ''Manga/BlueDrop'', a human girl and [[DiscountLesbians an alien girl]].
* ''Anime/PuellaMagiMadokaMagica'' has magic dependent on EmotionalPowers, so by the time of [[Anime/PuellaMagiMadokaMagicaTheMovieRebellion The Movie]]'s conclusion, [[spoiler: the powerful relationship between Madoka and Homura ends up being the cause of numerous reality rewrites.]]
* The second ''{{Drakengard}}'' game.
* ''Anime/EurekaSeven'' is a quintessential example, in which the blossoming love between a 14-year-old boy and a blue-haired HumanAlien literally saves the entire universe.
* ''VideoGame/LifeIsStrange'' revolves around the rebuilding of protagonist [[TimeMaster Max]] and her ChildhoodFriend [[TroubledButCute Chloe's]] relationship as they use Max's new TimeTravel powers to attempt to find out what happened to [[LivingMacGuffin missing girl Rachel Amber]] and prevent a storm from destroying their town. In the end, [[spoiler:[[PlayerPunch the player]] is forced to make a [[SadisticChoice choice]] between saving [[ButterflyOfDoom Chloe's]] life and allowing the storm to destroy the town, or [[TheNeedsOfTheMany letting her die so the town will live.]]]]