Hi!
I'm sorry about that, and thanks for reporting it. As there is no "Game Boy" option for the platforms selection on "itch.io", I decided to check all the platforms with Game Boy emulators available instead. But yes, the game is a native Game Boy ROM, and need an emulator to be played with (or a flashcart to use with an actual Game Boy console).
On Android, for example you can use RetroArch, a freeware application gathering emulators for many retro consoles, including Game Boy: https://play.google.com/store/apps/details?id=com.retroarch&hl=fr
That being said, I didn't intend to mislead anyone. So, if you bought the full version of the game and are not satisfied that it is not a native android application, I'll be happy to refund your purchase.