Letter and Japanese money from a Service Man

My father, John Martin Trimmer, was called up for National Service while the Second World War was still ongoing. He was an apprentice coppersmith at the time, and so put his skills to use by joining the Fleet Air Arm as an Air Fitter. He went out to the Far East on an aircraft carrier, and I have a photo of one that he was on board; I'm not sure if this was the only one. My research to date has left me unsure as to the name of the carrier, but the one in the photo with my dad among the ship's company was taken in Sydney Harbour in 1945. I believe it was taken in September, as I have a receipt for the photo dated 5-10-45. My research suggests that this was one of the carriers that then went on to pick up Japanese prisoners of war and return them to Sydney.

Upon my dad's passing in 1981, I also found among his belongings a letter from a mate in the services, also serving in the Far East. In the envelope with the letter were a number of Japanese notes (money). Although the letter was written after the end of the war in the Far East, I believe the story of the loan in the letter and why these notes were sent began before the final surrender. Also discovered were his discharge papers and a 'Neptune' certificate.