Soul Eater evokes memories of the first Fullmetal Alchemist for me. This shouldn’t be too surprising. Both are popular shounen manga that are serialized monthly, and even in the same magazine. Both have been adapted into anime by the same studio, BONES. Both adaptations have fantastic productions values. Both adaptations suffer from original content.
One of the problems that you run into when adapting an ongoing manga into an anime is that the anime moves faster than the manga. There are a number of hacks to get around this. I don’t think any of them have been well received.
The first way to do this is to attempt to animate the entire thing. The big, recognizable shounen series do this, like Dragonball and Naruto. The problem with this is that no matter how far ahead the manga is, the anime will always catch up, and when that happens, what are you supposed to do? The way this usually happens is by writing filler material, either before you catch up or when you catch up. This never works. In the case of Rurouni Kenshin, it ended the anime prematurely. In the case of Naruto, it caused almost two years of non-canon material, driving many away.
The alternative, which I theorize works better, would be to animate a season or two, and then stop and wait before animating any more. This was the approach taken by JC Staff with Shakugan no Shana. The problem with Shana Second is that they still ended up having to write bad original content even after waiting for a year. At this point, it’s not clear what they’re going to do with it, since they’ve written themselves into a corner and Shana is pretty popular. Otherwise, I’d say this is the best course of action.
There’s another option, which is to set a bound on the number of episodes, adapt as much as you can, and then fill the end with an original ending. This is what BONES did with FMA and Soul Eater. The problem with this approach is that the anime ending will be compared to what happened in the manga. In most cases, the manga will be superior in terms of development. This makes sense, since the characters have more time to undergo development and there’s more time to develop a more intricate plot. The other problem is that this closes the door on any adaptation of the later parts, unless you pull an FMA and remake the entire thing from the beginning.
Soul Eater suffers not because its anime-original end arc is bad, but because it’s not as good as what’s in the manga. Unfortunately, there is some really cool stuff that happens in the manga that we’ll likely never see because of the anime-original ending. The characters and the world get much more development and the events that take place are a lot less contrived.
It’s unfortunate that it’ll have to live in the shadow of the manga, because I really enjoyed the anime. The animation for the fights was awesome and the music, done by the guy who handled music for Gurren Lagann, was excellent too. Most of the disappointment comes from what could have been rather than anything it did wrong.