YOU SAID:
I am riding a bus in Japan
INTO JAPANESE
私は日本でバスに乗っています
BACK INTO ENGLISH
I am on a bus in Japan
INTO JAPANESE
私は日本のバスに乗っています
BACK INTO ENGLISH
I am on a Japanese bus
INTO JAPANESE
私は日本のバスに乗っています
BACK INTO ENGLISH
I am on a Japanese bus
You've done this before, haven't you.