A topic I’ve become fascinated with is games that are available in neither English nor Japanese (especially for non-PC platforms), since most games released on consoles are available in one or both of those two languages.
There’s a lot of games that are based on European properties, like game shows and children’s books.
Fantasia Sango II is probably one of the top of my lists of “want to play but can’t” along with Sword and Fairy’s 2 - 5 and most of the Xuan Yuan series