Edit: I did some research and apparently it’s a japanese mobile payment system that utilizes NFC. I found this on the GrapheneOS issue tracker, it seems to have been broken, but apparently it’s fixed now. Unfortunately I can’t try it out as I’m not from Japan. I also found this in the patch notes of a GrapheneOS version that was released in March of this year:
include PixelNfc app on all supported Pixels to enable support for FeliCa on Japanese Pixel models