Airbnb uses multi-currency processing. This is different from DCC in that the merchant asserts the transaction was never finalised in local currency in the first place and the currency is always in card currency.
It should be thought of as a hidden surcharge for doing business with Airbnb. No optionality allowed.
However I thought they have to present the price in card currency once during the transaction. If they have not prior to processing, reproduce your steps and chargeback Visa as reason Code 80 incorrect transaction amount, not reason code 76. The amount should be in yen as stated on the transaction page prior to finalisation, not whatever Airbnb says it is after.
Btw just had a DCC due to poor service. Had to buy some obligatory office souvenir snacks at BKK king power duty free. They set up overflow kiosks and I was directed to that. But payment has to be taken by main cashier. I stated "Charge Thai Baht" and the kiosk staff passed my card and invoice to cashier. When a long slip came out I promptly exploded, notwithstanding my mother standing three steps behind me this time. A void and recharge was promptly proceeded.