There are Trojan horse virus in apk file, my anti virus detect the virus type Android:Evo-gen [Trj], the obvious part is that the game need access to internal storage to be able to play it, so I doubt that it was a false positive.
I don't know what you mean to imply, but it is asking for permission to save because if you uninstall the game it would leave behind save files in case you decide to install it again. *Edit: This is a typical Renpy feature, meant for the PC, so I imagine it does not translate as plainly on Android.
As for the trojan, it's not like I have an official google or android app signature because it is not an 'official' game in the typical android sense. I'm not surprised it reports it that way. But it is a false positive.
If there was a virus that was doing anything malicious, and it is coming from my ONLY android link, wouldn't that mean there would be multiple reports of MORE than just the warning message?