What remains of you and me

So, this may or may not be inspired by another fanfic, I've searched everywhere I could think of for it, but I couldn't find it, I made a post on tumblr explaining what it was abt, so if any of you find it, please tell me.
I took the title from the game "What remains of Edith Finch".
This takes place somewhere between the beginning of the letter thing, and the beginning of the musical, so it won't follow cannon on anything other than Evan having to write the letters.
Would this count as a soulmate au, or a reincarnation au?
That is the question.