It depends completely on how they go about the refund.
If they have 200k bitcoins and decide to only offer cash refunds, then they have to sell 200k bitcoins, which will crash the market.
If they already have the cash and decide to refund in cash, then you have lots of crypto fans with a bit of extra cash in their pockets. That must result in extra buying, which would be good for the price.
I know that if I get cash, I'll probably put it back into bitcoin, if I get bitcoin, it will stay in bitcoin. The first is better for the price.
They are not dumb. They know perfectly well that's selling all the coins is going to crash the market. I am sure that they will try to return the callings as they are and if this is legally possible in Japan.