Not sure how you found the info of Sim card in the airport, we bought it from the counter and it cost around 25USD for 8 days with unlimited data access. It's pretty easy and smooth without issue.
Hi, thank you for your comment😊! I wish I hadn’t gone to the counter to ask about the SIM card prices 😂. Could you please let us know which mobile carrier you got your SIM card from? The one we asked about is Sakura Mobile, and they also have price guidelines on their website. The cheapest option we found was 3,500 JPY for 5 days 😂.