What's your favorite "springtime loss" film?

Summer Wars, a movie that I liked.

I don't reliably follow anime films (in the way that I do shows), so that one managed to slip by me. It looks pretty solid, thanks for the recommendation. :)

Ghost World is a great movie. I love comics and it's one of the few comic book adaptions that I've ever liked.

I love Ghost World. It's funny and sad at the same time.

Nope, that's a pretty standard coming-of-age film. :)
Going out on an adventure and learning from it is a fundamental of coming-of-age works, and is used to reflect the progression into adulthood. "Springtime loss" has coming-of-age elements, but is focused on lamenting and acccepting the loss of childhood [innocence], and thus isn't about entering the world, but on having the world forced upon you. Thus, standard active exploration-adventure elements aren't present in the genre (though as Girl Who Leapt Through Time, Arriety, and Marnie all show, reactive situations can be pretty adventure-filled in their own right).

Put another way, coming-of-age is typically about coming to terms with growing up and putting aside childhood for the sake of maturation, while "springtime loss" is more about enduring hard realities as the protagonists break from "the springtime of youth", losing their childhood innocence or being forced to put aside their sense of childhood wonder along the way. (One could argue that another distinction of non-springtime-youth works like According to Greta and The Perks of being a Wallflower is that such loss of innocence has, in a sense, already passed, but the individual has yet to come to terms with that fact by the movie's start. Thus, such films tend to ground themselves in more adult truths from the start, and focus more strictly on basic psychological considerations, without also offering the reference to metaphorical losses that "springtime loss" works offer.)

Finally, the "loss" element differs in Stand by Me, as loss in that film is just based in standard aging considerations. In "springtime loss", the loss has to be personal and significant, exemplified by a single event or experience, and representative of the loss of childhood.

It's a rather specialized, niche genre, but it's lovely- it embraces the innocence and sense of wonder of youth, and then shows those elements slipping through the protagonist's fingers.. finally ending in displaying the strength of the protagonist as they come to accept their loss, and what it means to move forward. Likewise, works of the genre always end on a hopeful note, implying the protagonist as still having a trace of remaining wonder (Arriety probably embraces that element the best), to indicate that not all beauty of childhood has been lost simply by the need to deal with life's harsher realities- that in growing up, we put aside innocence, but as we move forward, we also still can hold on to and appreciate the things we experienced along the way.
(Yet another reason Donnie Darko doesn't match to the genre: While you could argue a side character does present that note at the end of the film, it's far more bitter in the bittersweetness than examples of the genre ever are.)

In the end, I find the genre both the most poetic and the most beautifully inspiring of drama genres (and hopefully others will be able to better appreciate the genre after this thread, as well. ^.^)

(Also, as a side note, Field of Dreams makes an interesting contrast to the genre, in essentially being a 'Twilight Gain' work- where the works in discussion lament the loss of childhood and the need to put it aside, Field of Dreams (and similar works) lament the loss of childhood but attempt to reclaim its sense of wonder.)

That said, basically any coming-of-age-esque work is fine here- thanks for your input! ^.^

Out of curiosity, did you construct this genre, or is there information about it elsewhere?

I've been referencing the genre since the My Girl days (mid 90s), so by this point I honestly couldn't tell you. I know I've encountered the genre considerations and "springtime of youth" elements themselves in discussion, but I can't recall if I appropriated the label from someone else or if I constructed it myself from elements taken from more generalized discussions (which is something I've been known to do, in situations where I can't find an existing label to reference). Or, perhaps, it may have been a term local to where I grew up, which never made it to significant mention elsewhere. Google doesn't return any results for "springtime loss", so at the very least, my phrasing doesn't appear to be shared elsewhere.

Google isn't offering me any other labels to cover the genre, so either way- we can just start popularizing the subgenre here and now. ^.^

Well, I think I did a decent job in better detailing the considerations involved within the genre in my reply to heavenhairsixes above, anyway, so let me know if I left anything unclear. ^.^

In any case, Colorful is more in the vein of According to Greta and Perks of being a Wallflower, with a splash of Donnie Darko. In other words, it's more about dealing with enduring crappy life situations and coming to terms with yourself, than it is with losing innocence and coming to terms with the world.
I mean, I'm still gonna add it to my watch list, of course. :)
(If nothing else, this thread is getting me some solid anime film recommendations. :D)

or something you came up with?

No clue- but either way, let's hope it catches on more so that people start referencing it more frequently (and, hopefully lead me to similar films I'd otherwise have overlooked). ^.^