Kouhai Mario has finally been released in English. I opened the ROM in Lunar Magic and found there was already both Hiragana and Katakana...

https://www.dropbox.com/scl/fo/i9g6rul5zv8pcmiok9o9r/h?rlkey=1ajc068mqqscmlek4o05264zo&st=kvja916m&dl=0

Something's up with Kirby...