Hm, just from the synopsis, none of this seems to have anything to do with the concept of AoT. In fact, I wouldn't touch it, because I have to assume you will play off of some traits that are supposed to be known by friends of the franchise, but by saying this was for people wo "liked Attack on Titan" you're just inviting comparisons. It's basically made for no one - of course, there will be readers, no worries there, because some people know AoT and would still read stories, even if they have nothing much to do with it, outside of names. My point is that the attractive value is all over the place, because it's trying to address more people and ends up reaching less.
I think this story would Profit from being its own thing. The concept itself sounds super interesting.
However, it literally reads as if you just have to give the characters other names and nobody will realize it ever had anything to do with the aforementioned IP.
I also wanted to say that most "Reiner" are actually written "Rainer", but it seems from your description that it's an actual character from AoT that I have just never heard of.
Anyway, that's just my two cents. I originally clicked on it because I wanted to see what person still used the "If you like this, you will definitely like this™" type of advertisement.