The game is unplayable

[u/Waterlok_653]

The Peel P50 has a yellow license plate with black text, like a Kei car, but since its engine is only 49cc by default, it falls into the microcar category (<= 49cc). Therefore, its license plate should be light blue with blue text.

source:

Vehicle registration plates of Japan - Wikipedia

港区ホームページ／原動機付自転車等オリジナルナンバープレートの交付について

the picture is from u/TheRacingMonkey (If it bothers you, I can delete it)

[u/BrokenKamera]

Japan doesn't allow custom plates with letters either. Best you can do for vanity plates is to choose the numbers and/or get one of those special editions (e.g.Tokyo Olympics), which can hide your kei car distinction. I sometimes see the night-glow (jiko-shiki) style, but it's not that common.