With gratitude to Hakase's answer on Meta.Anime
In addition to the elements we've already discussed in How to ask a good story-ID question?, anime- and manga-specific questions that the poster could identify include:
What type of anime was it?
Did it feel like a feature film, a made-for-tv film (commonly known as an OVA) or was it a TV series or a ...
First of all, you should read the FAQ for the three sites (Anime, SF&F and Arqade).
After having done so, you may come to the conclusion that the question would only be welcome in one of them, in which case you have your answer.
However, you can come to the conclusion that it would be welcome in two/all of them. It's no surprise: there's bound to be some ...
If it's science fiction or fantasy, then it's on-topic here. Otherwise, it's off-topic. And if it's on-topic here, then it shouldn't be migrated or closed. The fact that a question may be on-topic somewhere else is irrelevant. (Indeed, another site that largely overlaps with this one is Movies and TV.)
On the Anime & Manga site, identification questions ...
Also did you allow this question because the anime is related to Fantasy or Scifi?
Yes these questions are definitely within the scope of the site.
No we should not migrate all anime content to anime.stackexchange. If that we're the case it could be argued that it is equally fair to migrate all sci-fi and fantasy content of other sites to this one.