Ignition is a Duo SI fanfic that crosses over Fate/Grand Order and Fairy Tale. Spacebattles members Leon/Writerwith badGrammar and Amelia/Aquirs-Chan wake up in the bodies of Avenger Edmond Dantes and Berserker Alter Jeane d'Arc (Summer version) in the world of Fairy Tale. You don't have to be really all that knowledgeable about either crossover to like the story though, because of its trashy premise, it has some very good writing. The SIs are written pretty well, and the writing isn't particularly awkward (though the characters are very socially awkward, as you'd expect a couple of nerds to be). The story was posted just two months ago and is still currently updating.