If you click on the link, it will download a .apk file. It is the game file for android... you need to run its file on your phone. We can't put it directly in the Play Store because of the +18 content.
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Ahhh! that's because the RPG Maker (the game engine of the game) exports the Android version to use a web version... so... we have the web version... the Android downloads the maps on demand from the web version... and let it in your phone... when we update the web, it download the changes, so you don't even need to update the APK. Just in case we switch our webserver.