I've worked in the video game industry for a while and when you deal with a customer that claims that they lost currency or items due to a bug, they should be compensated as fast as they can. An online game like this has to have a database that stores all the information about when a player spend currency and what they spent it on. If they claim that they spent unwillingly currency on some stuff, it should be easily retraceable. Even if you don't know the intent of the player, if he wanted or not to purchase this, if a bug made them purchase that or not, shouldn't matter for a refund. iOS and Android refunds their customers for any In-App purchases made in any application no questions asked, and that means the player will still keep the items or currency they got with that transaction. It just make sense that the customer should have the best experience possible when these situation arise, especially when your user is a recurring spender in your app. Of course, some people could exploit this flaw in how the system work, but this is the first time Kira is asking for any compensation, even after spending some money over the last year. Even so, he is willing to have the items he didn't mean to purchase being removed from his account.

There is also the fact that Kira isn't the only person that claimed to have this bug happened to him, so there should be even more red flags when dealing with this. Not resolving this, might not only prevent those people from ever spending ever again in the app, but everyone that note how bad you are managing this issue as well.