An international couple may get divorce by mutual consent in Japan. It is, however, risky to get divorce merely by mutual consent. This is because their marital assets may be located outside of Japan where the divorce by mutual consent is often not recognized and/or enforceable. To avoid the risk, it is advisable to get divorce judicially.
Please see the attached explain the detail of how to get judicial divorce.
international-divorce-between-foreigners_enforcement-of-divorce-in-japan