Maybe come up with a 3 months subscription package or something along that line and reward those who pay the 3 months subscription upfront with additional candies for free. You can use the leftovers you have or other unique Japanese products that people may like. This way you're assured that you have subscribers for the next 3 months.

Or instead of giving away free candies to the package I mentioned above, reduce the price to say $20-$22/mth if they pay upfront for 3 months to give them the $6-9 savings over 3 months.