I would keep them mainly restricted to the Asian/Pacific theatre. Although they would not be doing too much after capturing Tsingtao.
However, the IJN did send ships to the Mediterranean (a destroyer flotilla with one cruiser as leader) to work with the RN out of Malta and even had one torpedoed by an Aus-Hun U-boat, and some of their heavier units escorted troop ships from Australia and New Zealand to the Suez. They also participated in searching for the German East Asian fleet and the raider Emden. And finally they even transferred 12 of their destroyers to France.