OMG, this worked! Uninstalled the Lunateria (demo) and it let me install TToF! :)
...Now if only the creators of both games would update the names, this wouldn't be an issue... :-/
Well... Technically you can install both. But is required for you as end user, to change Android Manifest in one of the packages, using tools for viewing and editing *.apks. And you must resign it with developer signing keychain. And Android will definetly say that resulting apk is dangerous (because test signing keys).
(plus I remember to been having a real headache when I was doing it, although I don't remeber exactly how I managed to make it work)
Too much work for such small outcome :)
Oh, and BTW - there is a tutorial for how to make android package with Renpy AND set an actual package name right (under Step 3)
https://lewdpixels.com/features/building-your-own-android-a-renpy-howto/
...Meh, losing access to a (somewhat outdated) demo so I can read an on-going VN isn't a big deal and, as an end user, doing what should be the job any half-decent creator(s) should already be doing anyways in order to regain access to said demo I wasn't planning on playing through again (but, admittedly, was too lazy to uninstall, since it wasn't really taking up any space) isn't really worth that much effort ('specially by the end user in the situation) ¯\_(ツ)_/¯