For a full refund with no refund fees, you must request a refund within 24 hours of purchase.
After 24 hours of cancellation, you must pay refund charges based on ticket type and flight departure. The refund charges will be subtracted from the actual rate and you will get a refund for the remaining value.
Non-refundable tickets will earn travel credit that can be used to purchase future flights after subtracting refund fees, if applicable.
If you used a portion of the ticket, you will get a refund only for the unused portion of the ticket after subtracting any refund charges.
If you buy the ticket with the travel agency, you can contact them to process the refund after the cancellation of the flight.
Japan Airlines Cancellation Policy says if JAL cancels the flight at the same time as your departure, you will have to pay a fee. This fee can vary from $100 to $400 depending on the destination and ticket type. But, when you are in a no-show situation, you don't board the flight and don't inform the airlines about it. In this case, your ticket charge will be equal to the cancellation charges, i.e. no refund for such condition.