I'm travelling from Croatia to Japan in September and I'd like to know if there are any fees I have to pay along the way? I'm travelling Rijeka-Stuttgart-Frankfurt-Kansai and then Kansai-Haneda-Frankfurt-Hamburg Rijeka on the way back. I don't know if there are some special airport fees to pay that aren't included in the ticket price?
Airport fees are normally included in the price of the ticket. Having to pay them at the airport belongs to those days of carbon paper tickets. Unless Croatia has special rules, a holdover from the 20th century, you shouldn't have to pay anything. I just came back from Tokyo via Haneda and they didn't ask for anything.