-UK keeps ties to Japan following takeover of Manchuria and offers them oil out of Arabia
-Japan decides to try to gain oil from multiple sources instead of just USA and believes treaty with UK will help if USA is a problem
-No Marco Polo Bridge incident, no rape of Nanking, but plenty of Japan playing warlords off of each other, especially in Southern China/Guangzhou/ Shanghai areas
-French Indochina falls under Japanese "management" and is leased out until war's end
-UK calls on Japan for help, Taranto is destroyed entirely by a combined UK/IJN task force. Japan amasses troops in Egypt and naval forces make El Alamein really interesting. German forces whelp the Imperial land forces, but air superiority goes to Japan with precision bombing. Naval dominance crushes German positions as if they were cardboard. Army forces realize that without some sort of tank force they are outclassed in large-scale battles and borrow older British designs.
-Japanese ground forces are instrumental in cleaning up North Africa and naval forces cut off retreating Germans at Tunisia, leading to over 250,000 surrendering Germans the day USA enters the war. German war material is sent home to Tokyo for analysis and testing.
-Japanese landings in Sicily, now backed by British tanks, take the islands quickly. Greener American troops land in Italy and get trounced but are saved by Japanese assistance in Calabria.
-By war's end in 1944 the Japanese are producing tank prototypes roughly equivalent to the Pershing of OTL and early jet designs. Small arms are upgraded to an M1 knockoff though the Stg44 will soon "inspire" new designs as well. Her industial capacity and shipping are improved from 1941 and her relationship with the UK continues to prove valuable, as a reward Japan is given an occupation zone in the Rhine which she strips of talent and industrial equipment before combining with the American, French, and British zones to make Western Germany in 1946.
-Japan also cleans Communist influence in China after the war and sets up a puppet state in the South (Shanghai), one in the Center (Chongqing), one in the northeast (Beijing), and one in the northwest (Urumqi). It also sets up its Greater East Asia Co-Prosperity Sphere under the guise of decolonization but uses economics instead of direct occupation as a means of control. Her navy is the third largest in the world and her technology, military, and overall industrial capacity are greatly improved by involvement with the Allies.