Part of the plot of the film revolves around the Type 91 torpedo, and the fact that it was given to the Imperial Japanese Navy by the Germans. Although the Type 91 was a real and highly effective aerial torpedo in use by the IJN during World War II - it was used with devastating effect at Pearl Harbour - it was not a German design. It was developed by the Japanese themselves back in 1931, and went through various modifications and improvements until its use in World War II, including the addition of wooden stabilising fins for use in the shallow waters of Pearl Harbour. It also doesn't make much sense for the Japanese to only get the weapon two months before launching their attack, because that would have given no time for further development and modification for Japanese torpedo bombers, or for training pilots in its use.
Historically, there actually was a real exchange of aerial torpedo technology between Germany and Japan, but it was in the opposite direction and only in 1942. The Germans had no good aerial torpedoes of their own, having previously bought ones from Italy. The Japanese sent some examples of the Type 91 to Germany via submarine, where the German version entered service designated as 'Lufttorpedo LT 850'.
