If there's one thing guaranteed by a successful anime franchise for TV, it's the fact that somewhere down the line a spinoff film, or a whole gamut of them, will be produced for the big screen — or for the little one, in the form of an OVA. No fan in their right mind complains about this state of affairs: who gripes about getting more of a good thing? But more is not always better — or rather, the mere fact of getting more isn't what matters most.
Don't take any of this as a sign that I'm somehow out to shame people for enjoying spinoffs. I'm not. In fact, I'm writing this because the problem I have with spinoffs is something that prevents me from fully enjoying a product which is often a pretty good movie in its own right. The very nature of a spinoff means nothing that happens in the film can possibly matter, that nothing's ever actually at risk, and so everything we see is ultimately just a holding action before everything returns to the status quo of the original series.
Most every spinoff film follows the same basic pattern: it's a side adventure, something that takes place during some point in the original story's main action. A great deal may happen, but only on closer inspection do we realize nothing has in fact happened — we're right back where we started in terms of the larger story being drawn upon.
What's worse is how this is an immutable condition of such side stories. There's no way for them not to end up negating themselves.
The problem of the riskless narrative
With the main story, risk is a given. In the abstract, anyone can die — and if you're talking about a series like Death Note, that's a gruesome inevitability. But even in shows where the core characters are more or less blessed with narrative invulnerability (because without them, there's no story), there's a degree of risk present somewhere.
With spinoffs, the only real risk is with characters who are introduced specifically for the sake of the side story. They're the only ones who can actually be endangered. And there we run into another problem: the more we feel for them, the more the story works to make them fully fleshed-out and sympathetic, the more frustrating it becomes, because then the more the source material just becomes so much baggage to be dragged around.
This particular problem reared its head most prominently with Fullmetal Alchemist: The Sacred Star of Milos. It's one of the better side-story films you're likely to find for a major franchise, in big part because it brings us two very well-developed standalone characters, Ashley and Julia Crichton, and makes us give a damn about them. So much so, in fact, that Edward and Alphonse end up being the tail(s) wagged by the rest of the story's dog. So much so that we wonder why the encumbrance of the Fullmetal Alchemist franchise wasn't just jettisoned entirely and the story developed as its own work. (But then we wouldn't have had the brand-name recognition of the franchise, and its consequent sales, I guess.)
The same things happen, more or less, in a spinff that was released in English shortly before I started this essay: Naruto Shippuden: The Movie: The Lost Tower. The most we can feel for Naruto is that he will somehow prevail, which is no less and no more than what we ordinarily feel for him. As for the one-shot heroine of the film, Sara, everything we feel for her is going to be limited by the way the single-instance nature of the story is forever at odds with the longer story it was derived from.
Fanfiction should be left to fans
One possible defense of this sort of storytelling is that it's a way to tell a specific kind of story — one about our hero meeting someone along the way during his larger journey, having an adventure with them, and then parting again. We need not return to them again, for parting is such sweet sorrow and all that.
Fair enough. But that still isn't compensation for how the larger story typically isn't served at all by these sorts of side jauntes. Rarely, if ever, does anything that happens in them become full-blown canon in the main storyline. After a while, it becomes hard to watch any one of these productions without feeling like they're simply sanctioned fanfiction of a sort. This isn't to say that fanfiction is a bad thing — it's a vital way for a fandom to bond with a show and do everything from celebrate its excesses to comment on its intricacies. But maybe that sort of thing is best left to the fans.
That said, no philosophical issues I have with spinoffs will prevent them from getting made, distributed, and enjoyed. They're as much a part of the anime experience as any other aspect of it. I'd be lying if I said I hadn't enjoyed many of the spinoffs I've watched.
But compared to the joy of watching the source material, the pleasures I get from spinoffs always seem ... well, hamstrung. With a spinoff, everything can only go so far, nothing can ever be really changed, and in the end it's not even clear anything's actually happened at all. Why devote our time to something only to have our hands close on thin air?