This Japan expanded very fast in WW2 after the attack on Pearl Harbor, as IOTL, although the USA who didn't have to fight against the Third Reich fought them successfully back since May 1942. They managed to invade Bengal in September of the same year and even landed on Ceylon in October, but now they had reached the maximum of their expansion and were slowly driven back by the Allies. In spring 1945, they landed on the Japanese home island of Shikoku. Japan gave up after the USA dropped the bomb on Niigata and Nagasaki in September 1945.
Japan was allowed to keep the emperor, but had to give up all the colonies, Okinawa, Sachalin and the Kuriles and accept the American occupation.