If you access the mysterious door to Nekoya's restaurant which spawns randomly in the world, the charges of the ring reset.
This is the only way, which is pretty useful in the end game (which is also when the door is more easy to find as more regions are unlocked).
Three is the
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quantity of charges, although the ring does not fully work like it does in canon.
The game is also balanced around three charges, being quite easy at the beginning of the game and gradually getting harder to manage in the end game if you are pursuing a harem.