This is the 787th most frequent Ukrainian word.
японії
"Японії" means "Japan" in the genitive case in Ukrainian.
Here, 'Японії' is used in the genitive case to indicate the destination of the dream.
Я мрію про подорож до Японії.
I dream of a trip to Japan.
In this context, 'Японії' is in the genitive case showing possession, belonging to Japan.
Культура Японії є дуже цікавою.
The culture of Japan is very interesting.
'Японії' here is used to denote origin or association, again in the genitive case, as it describes the languages associated with Japan.