Anime fans HATE filler. In fact, it's amazing how the community can be so united in their hatred.
But as much as you might despise it, it is a necessary evil and sometimes makes an anime 10000x better.
Gintama does a good job explaining filler basics:
That's a lot of gifs but to sum up – filler in anime has to happen because of two reason:
- The manga is nowhere near completion, so the anime has to diverge.
- Japanese TV stations are strict about contracts (26 episodes means 26 episodes), so you need filler to meet airing requirements.
Certain Anime Would Not Exist
Crazy idea, right? But, if we went by the community's reaction towards filler, entire anime would not exist.
K-On! is one of the most popular and financially successful anime of the modern era…and it's all filler. 99% of what happens in the anime is not in the manga, and there is good reason for this. K-On! is a yonkoma manga, meaning that each chapter only uses four frames to tell jokes.
Yonkoma manga does not provide a lot of content to adapt.
The relationships, concerts, and character growth over the course of K-On! was made possible because Kyoto Animation expanded on everything. Essentially, the anime is only K-On! in name, and fits the strict bill of being "filler".
If we went by the popular mantra that nothing should be added to the manga, then K-On! would not have existed. In fact, no anime based on yonkoma manga would be possible. Would you want to live in a world without Nichijou, Working!!!, or Monthly Girls' Nozaki-kun?
The same argument can be made for video game and light novel adaptations. Events need to be re-worked or removed, because what works in a game will not always work in an anime.
Most Anime Would Not Have Closure
The biggest flaw in adapting a currently popular manga is that they tend to be nowhere near ending.
When adapting a work like Noragami or Soul Eater (at the time), the studio has to make a tough decision about how to end the anime. Not all arcs have a clean stopping point, and if a second season is not guaranteed, you don't want to give fans false hope.
But if the current arc does not allow for this, you get what is called a "gecko ending". The last 3 to 4 episodes of an anime, like in Noragami, may switch to a quick original arc to provide some sort of closure. If a second season is picked up, the gecko ending is easily ignored.
In most cases, an ending that provides some sort of closure is better than a non-resolved cliffhanger…right Rokka: Braves of the Six Flowers?
The Manga Creator is Okay With Filler
Yep, sometimes the things fans hate is something the creator is perfectly fine with.
A famous example is 2003's Fullmetal Alchemist anime. Hiromu Arakawa, creator of Fullmetal Alchemist, told studio Bones to create their own story after they ran out of manga material. In an interview with NewType USA, Hiromu gave her thoughts on filler, saying:
“Manga and anime are different modes of expression, and different artists are involved. There’s little point in having a cross-media story if everything is exactly the same in all versions.”
This is the same view Hideaki Sorachi has about the Gintama anime. Certain jokes and parodies only work well within their respective medium, so it's a matter if fit instead of being "faithful".
The World Would Be Missing This Scene
The world is a better place because of Kakashi's fish lips.
It's true that when filler is bad, it can ruin the flow of a series. But just because something is filler does not make it bad by default. Sometimes those original arcs or episodes are necessary in providing a solid anime experience that aligns with the source material or fulfills the anime contracts the studio signed.
Anime is an industry adapting the hottest and most current manga, visual novels, light novels, or game. Unless there is a shift adapting finished works, which probably won't happen, then we have to accept that filler will always be with us.