Tsundere Appeal: The Difference Of 10
OK, this article has been sitting around on my website, unpublished, for over three years even though it's basically been finished for six months.
So, for a while, I wasn't sure what the big deal was with the "tsundere" anime-character-archetype. Even aside from the whole "different people like different things" thing, I couldn't figure out precisely why it was so widespread. It actually took me several years to figure this out and finish writing this article, but I now have an explanation which I fully understand and which is backed up by SCIENCE.
A tsundere, by definition, is a female character who alternates between being aloof or aggressive (the "tsun" part), and sentimental or affectionate (the "dere" part). In practice it's usually a female character who refuses to admit to anyone that she is in love with another character, when it is flagrantly obvious to the audience (and perhaps the rest of the cast, usually excluding the object of her "affections"). Either mood can be her default one, and they usually behave more "normally" around other people, but the end result is the same. The best-known Western example is Helga from Hey Arnold. The first example I ever encountered was Tron Bonne from Megaman Legends.
Some people like them a lot. I mean, if you just say "tsundere," such a person will go "Ooh! Where!?" I really didn't understand this sentiment at first; I have a habit of trying to come up with explanations for Why People Do Things, but for a while, this one had me stumped. None of the reasons I came up with (e.g. "You're awfully cute when you're angry"/"same as if she's just playing hard to get") really satisfied me, and nobody who did like them could coherently explain it to me. I mean, yeah, I could understand why people liked the "dere" part, but not why they put up with the "tsun" part, let alone were attracted to it. In fact, as you may recall, I had started to find it annoying, especially when the character in question was static and never developed into something better, and/or when fanfic-writers took a preexisting character and replaced their personality with "generic tsundere." It didn't help that no two people consistently used the term the same way. However, I believe that I now grok the concept enough to articulate the reasons for the concept's popularity.
It's actually quite straightforward: your first impression colors your overall opinion. If your initial opinion of someone is that they're aloof and cranky and confrontational, and they start to become more pleasant by any degree, you view this relative to your first impression rather than objectively. When they start acting full-on affectionate and bashful, your perception is of the difference between that and the original behavior, rather than the difference between that and "neutral." To put it another way: when someone goes from -5 to -1, you percieve that they've gone up by 4 even though it's still in the negative, and when it goes to a positive 5, the total difference is 10. This makes you percieve them as "better" than if they started at the 5 to begin with.
This was demonstrated in a study by psychologist and anime/manga fan Yoshihito Naitou.1 Given the choice between video clips of 1. someone who acted nice the whole time, 2. someone who started nice and turned mean, 3. someone who started mean and turned nice, and 4. someone who acted mean the whole time, #3 was the overall favorite.
Besides which, tsundere characters are pretty much all cute/attractive. (The creator of a tsundere certainly wouldn't deliberately make an unattractive character.) In particular, on the rare occasions when someone actually calls a tsundere on her tsun-BS, she tends to blush in an oh-so-adorable manner, if it doesn't actually straight-up trigger the "dere."
The other factor is what's known in psychological circles as classical conditioning. Ivan Pavlov is famous for making dogs salivate at the sound of a bell; with repeated exposure to the correlation of "bell ringing" and "food," their brains made the connection that bell = food, and so the bell made them salivate even when there was no other sign of food. Much in the same way, anime fans (or at least tsundere fans) have begun to mentally associate the entire concept with the emotional response they get from the relative-"dere." In short, the anime fans have begun salivating at the sound of "I-it's not like I like you or anything!" before there's an actual dere-"payoff."
A side effect is that some recent anime shows feature "tsundere" characters who never show a dere side; all you need to do is present a character as a "tsundere," and let Pavlov take its course. It saves the producers the trouble of creating a well-rounded multidimensional character, so it's a win-win for everyone except the critics, and who cares about critical success when you've got financial success!
"Treat 'em mean, keep 'em keen" works brilliantly when it's an anime character doing it, and if your fans have been trained to associate the two halves of that saying with each other, you can dispense with the "keep 'em keen" part.
1This is how I finally learned to understand the tsundere appeal, even if I still don't share it.