pixiv PAY is a payment app that allows buyer to pay by reading the QR code.
For settlements, you can use a credit card registered in pixiv PAY, as well as card info registered in pixiv and other services managed by pixiv.
In addition, since cash payments are also available, you can also display the total amount of the items you purchased and have access to a "cash register", where you can record the number of sales and the profits.
You can shop at doujinshi events without having to carry large amounts of cash with you! Also, sales are transferred to your bank account. If you're a seller, you won't have to carry cash with you back home!