It is now possible to play Moonstone Island on Android and Apple iOS devices, as Studio Supersoft and Raw Fury announced the game ended up being added to Crunchyroll Game Vault.
Moonstone Island is available on the Nintendo Switch and PC, and you can play on mobile devices in subscribed to a Crunchyroll subscription tier that includes the Game Vault library.
Here is the official trailer that shows how Moonstone Island looks if you play the game on a mobile device.
As a reminder, only two tiers qualify for the Crunchyroll Game Vault access.