"My name is Misaka Mikoto! Learn it already you idiot!" - Misaka from Toaru Kagaku no Railgun
Tsundere (ツンデレ, pronounced [tsɯndeɾe]) is a Japanese term for a character development process that depicts a character with a personality who is initially polarized warm/soft, cold, temperamental, hotheaded (and sometimes even hostile) before gradually showing a warmer, friendlier side over time.
The word is derived from the terms tsun tsun (ツンツン) ('to turn away in disgust or anger') and dere dere (デレデレ) ('to become affectionate'). Originally found in Japanese bishōjo games, the word is now part of the otaku moe phenomenon, reaching into other media such as maid cafés, anime, manga, novels, and even mass media. The term was made popular in the visual novelKimi ga Nozomu Eien.
Where Did The Term Tsundere Originate From?
Like many anime fan pieces of terminology, the root of tsundere lies in the bowls of dating sim lingo. On a Japanese forum for dating sims way back in 2002, fans were discussing the game Kimi ga Nozomu Eien, specifically the character of Ayu Daikuuji. One fan commented that they liked how they had to work past the "tsun tsun" harsh side before they could get to the "dere dere" softer side. Other forum members liked the turn of phrase and soon the phrase "tsundere" was being used across forums to describe girls in other dating sims with similar characteristics.
That's not the only significant claim to fame for Kimi ga Nozomu Eien either. The game eventually spawned the spinoff Muv Luv, which in turn morphed into the mecha alien-fighting apocalypse Muv Luv Alternative, which Attack on Titanauthor Hajime Hasayama said was one of his biggest influences. So that one little dating sim, mostly forgotten amongst English-speaking anime fandom, can claim both tsundere and Attack on Titan as spawning from its influence. Quite the legacy it has left.
How Did The Tsundere Boom Catch on Overseas?
English speaking anime fandom soon caught the tsundere fever going around. While people who could speak Japanese were doing the diligent work of telling everyone who would listen about this new term anime fans in Japan were using, it didn't take long before the anime themselves started using the term (the earliest example I could come up with was Tsuyokiss, but I'm sure it appeared before then). Rin from Fate/stay night, Shana from Shakugan no Shana, even some of the discussion about Kaname Chidori from Full Metal Panic started including the term tsundere in English speaking fandom. As the term gained further acceptance and exposure, it started to be referenced in everything from video games (see Undertale), fan-fiction, and some very strange memes. Go google tsundere sharks on day and be amazed at what you find.
A Quick Guide to Dere Types
The term tsundere became so popular that soon fans started to use the formation of the term to describe other dating sim character archetypes (yes, we're still mostly in the region of dating sims here, where all anime girl trends are born). Almost all of them use the "dere" ending to describe the cute side you see, with something else put in front. In English, the term "gap moe" has been used as a catch-all term for this, signifying the nice surprise you get when a character who usually displays one emotion suddenly displays another, highly contrasting one. Examples of this include:
Yandere: Certainly the most famous derivative, where a character appears cute on one side only to reveal she's a crazy person who will slice your head off with the nearest axe if you get in between her and her "true love", which is where the "yan", or love sickness, part comes from.
Kuudere: A character who is usually all cool, or "kuu" (no really, that's what the Japanese call it), and composed, displaying little to no emotion, but then displays hints of their softer, more lovestruck side.
Dandere: A Japanese homophone that has two different meanings. The most popular definition of the term comes from the abbreviation of "danmari" - which means to be calm or quiet - and "dere". Then there is the more uncommon "dandy" + "dere" theory, since the Japanese have a weird love of this otherwise outdated English word. Anyway, the dandere usually refers to the shy one who will never speak up until you finally get her alone and talk to her, allowing her to spread her "dere" wings and soar into your arms.
Tsundere Characters
Asuka Langley (Neon Genesis Evangelion)
Asuka Langley is a classic anime character, being a 14-year-old girl who can pilot a massive EVA mecha. She is a German girl with some Japanese heritage, and makes for a rambunctious teammate for Shinji and Rei.
True to tsundere form, Asuka is self-absorbed and keeps people at arm's length, but sometimes, she'll show her vulnerable or friendly side (though not for long). There was even a time she practiced kissing with Shinji, though she felt a bit let down by the results. Oh well.
Aisaka Taiga (Toradora)
The trend of tsundere blew up in harem anime throughout the late '90s and early '00s. But the face of the tsundere from 2005 onward became a voice actress Rie Kugimiya. Shana from Shakugan no Shana was the original but it became supplanted eventually by her role as Aisaka Taiga from Toradora.
Toosaka Rin (Fate/stay night)
If you want the face of the tsundere within anime fandom today, it would probably be Rin from the Fate/stay night. She acts haughty and arrogant, using frequent put-downs in her conversations, but blushes frequently when someone acts with a friendly disposition towards her.
Makise Kurisu (Steins;Gate)
You know what's better than a regular old tsundere? A tsundere that's really goddamn smart! How about a scientist who skipped grades in school and publishes papers that affect research conducted in CERN that gained her international fame within academia before she had turned 24? That's pretty goddamn impressive, on top of the fact that she's cute and blushes when you tease her.
At some point the fans of anime who were going nuts over tsundere became writers for anime themselves. At which point they started deliberately inserting tsundere into their anime and calling the characters out on it in self-referential styles. Fandom language became codified by the anime themselves. For a classic example of this, see Makise Kurisu in Steins;Gate desperately refuting accusations that she's a tsundere. Which is classic tsundere action in itself, a catch 22 for poor Kurisu.
Kagura (Gintama)
For the most part, Kagura keeps herself aloof from her companions, and she isn't too quick to show her warm and friendly side. This is a comedy anime, after all, not a romance. There's too much wackiness going on for a love story, alas.
Isla (Plastic Memories)
And now, for a truly tragic figure... the Giftia (android) Isla! In the world of Plastic Memories, Giftias are highly realistic companion robots who serve as computers and friends to anyone who needs them, but the only live so long. Soon, they must be collected and taken away to be shut down before their programming gets frazzled.
Isla's job is to help retire other Giftias, but her time is running tragically short. During this time, her new co-worker Tsukasa takes a liking to her, and he's desperate to keep her alive and functional. It's a futile effort, but it's wonderful to see Tsukasa give Isla a deep and real friendship right up until her last moments. In fact, she "dies" in his arms atop a Ferris wheel. At first, Isla wanted no friendship of any kind... but later, it was all she ever wanted.
Erina Nakiri (Food Wars!)
This tsundere demonstrates some excellent personal growth in more than one way. Erina Nakiri is near the top of the culinary world, being the grand-daughter of Totsuki Academy's esteemed dean, and her cooking skills and sense of taste are peerless. She's cold, though, and this is partly because of how her oppressive father treated her.
When Erina meets the cheery and optimistic Soma Yukihira, that icy exterior melts bit by bit. Erina can't stand Soma at first, but time and again, she has his back as he takes on the most talented chefs in Japan. Near the series' end, she is his trusted teammate in a team Shokugeki (cooking duel), and she even borrows Soma's goofy trademark visuals when she serves her food! The happy girl we knew in her past is back at last!
Kirino Kousaka ( My Little Sister Can't Be This Cute)
Once creators started to become more comfortable with tsundere, they started combining character archetypes to create new and interesting formulas. The creator of the hit light novel My Little Sister Can't Be This Cute decided that the little sister character needed a revamp. Too long had they been shy, subservient and clingy. With Kirino he created a tsundere little sister. However this turned out to be like combining bleach and ammonia and created a character who is literally worse than smallpox.
Kaname Chidori (Full Metal Panic)
There was a time when whacking your love interest with a folded up paper fan was a hallmark of abusive tsundere relationships. That has long since died down, but with the announcement of a new Full Metal Panic anime recently, perhaps it's time for Kaname Chidori to bring that fad back into vogue.
Haruhi Suzumiya ( Suzumiya Haruhi no Yuuutsu)
Considering tsunderes are pent up balls of frustration who lash out whenever they find themselves incapable of expressing their feelings, perhaps it's not so great that an all-powerful yet unknowing god is a tsundere.