1. Mashima is collaborating with the fillers is because he didn’t want to do the same as Naruto, One Piece and Bleach do with their filler arcs. He didn’t want the animators adding stuff that were of no relevance to the manga at all and that could even ruin the story. I also read that he’s strenghtening the relationships between the main pairings in the anime, because of what is about to come in the upcoming chapters, so that it wouldn’t feel too forceful when it came to it.
2. THE ANIME CAN BE CONSIDERED CANON, SINCE MASHIMA SAID HE WROTE THE FILLERS HIMSELF.
3. The only fillers that Hiro didn’t write were the NaLi ones. The director had told Mashima to bring Lisanna back, because he liked her character a lot, so Mashima did so, that’s also…Read more >