I enjoy second chance fanfic, AU, time travel/time loop/future vision, self insert and Crossover fics where a character who faces a tragic fate in canon is saved from it in the fanfic. I like happy endings which is why I love fanfic so much. Anyway, I'm basically looking any fics where the MC's main goal/focus is to save someone from a tragic fate/circumstances.
I think the canon in the request is something different than the cannon in cannon fodder. Canon means the main plot line in manga, not sure though.
I've got a lot of these. Hmm, the first 3 match your criteria. The next 3 are alternate universes with a better future. Muv Luv: One Last Time Into the Loop (Muv Luv) - https://www.fanfiction.net/s/7112821/1/Muv-Luv-One-Last-Time-into-the-Loop From Fake Dreams (Fate/Stay) - https://www.fanfiction.net/s/7207791/1/From-Fake-Dreams Once More With Feeling (FFVII) - https://www.fanfiction.net/s/4813784/1/Once-More-With-Feeling Path of the King (Fate/Stay) - https://www.fanfiction.net/s/7657235/1/Path-of-the-King Code Geass: The Prepared Rebellion (Code Geass) - https://www.fanfiction.net/s/10724053/1/Code-Geass-The-Prepared-Rebellion-V2 Stand Together and Smile (SAO) - https://www.fanfiction.net/s/12894463/2/Stand-Together-and-Smile