Most people don't actually use the NFC, It's just not as highly accessible in North America as it is in other places (Also, very specifically, Amiibos will not work, and this is an in-game notification as well. No idea if this was a licensing thing or what). It's an interesting gimmick to replace how Swapping out CDs worked for the original Playstation game, but most people use the Keyword generation in the North American version.
Thankfully, we solved how keywords worked. After scripting out auto-solving more than 2 million keywords, and filtering out duplicates, we have published options for every baseline, and every variant (stuff that has different stat gains, starting stats, starting techs, or faster guts regeneration from the baselines).
Keyword Solver for manual entry of any keywords you want, to see what it will produce
Curated list of Keywords: Pick a Kaiju main, then Kaiju sub. Below the choice will be a scrollable table of all the Script-found Kaiju and fan-submitted Kaiju
NTAG scanning and Bus Passes are solved too.
The bus passes are fun/interesting because the remaining balance of Yen on them is what determines what it makes. Many of the numbers are references to Ultraman or Monster Rancher lore. If you're curious about that, check out: https://legendcup.com/faq-ukmrnfc.php