Here's the challenge, have Japan be part of an alliance that matches OTL's Anglo-Japanese alliance in length (20 years) with a different partner than Britain or the United States (after all US-Japanese alliance is 66 year old alliance).
So instead, have at some point in the 20th century a long-lasting, two decade Japanese alliance with Russia (form of government, monarchism, militarist, republicanism or communism does not matter), or a two decade alliance with France, or with Germany.