Story Challenge
Nasuverse/Animorph Crossover
Here's the idea the Yeerks are planning something in Japan so the Animorphs head over there to try and stop them. They stay with the family of one of the Animorphs who lives in Fuyuki City. They start searching for the Yeerks but are ambushed by them and just as it looks like they might die one of the Animorphs (who is up to you) accidently summons a servant who promptly saves them (who that servant is, what class they are, and how they save the Animorphs is up to you). The servant then introduces their master to the Fifth Holy Grail War.
Show the Animorphs as they go through the hell of the Holy Grail War and how their discovery of the existence of magecraft and shadowy powers hiding it from the general populace affects the Yeerk invasion. I would recommend keeping all the masters that fought in the cannon Fifth Holy Grail War along with Saber and Archer, but its up to you. Also I would recommend switching between the Animorphs perspective and Shirou or Rin's perspective. For the Animorphs this should be after Ax joins the Animorphs, but before the Yeerks discover the identity of the Animorphs. I would also recommend that neither the people on the Magecraft side of things nor the Yeerks are aware of each other (though either side might not a hidden organization whose agenda some times comes into conflict with their own). Also I would prefer if this not just stop at the end of the Fifth Holy Grail War but that it continue and show the Holy Grail War effected both the Animorphs and the (surviving) masters (and servants if you so choose). Show how the Magus Association, Holy Church, and Dead Apostles (Ancestor or otherwise) discover and react to the Yeerks and vise versa (one thing I would like to see is the eventual general revelation of magecraft and aliens to the world,though probably not till awhile after the Fifth Holy Grail War).This should not stick to being a solely Fate/Stay night and Animorphs story, but should instead cover the whole of the Nasuverse as well.
I will post the address to the story of anyone who takes up this challenge though I do ask that anyone does notifies me about it.