According to "Steel in the Deep" on internet which was made by old Japanese navy related people (it is written both in Japanese and English. I got necessary information for this article from its SiD the Submarine Project.), the question whether Ensign Toshio Mizui had Chief Master Sergeant Akira Nakai as his co-pilot when he attacked the enemy transporters on August 12, 1945 or Chief Master Sergeant charged against the enemy riding on the separate ship was not cleared. On August 12, 1945, two days after Mizui's attack, Chief Master Sergeant Yoshiaki Hayashi made an attack alone on Kaiten. At thar time I was a student of university but I was mobilized to work at Kure Naval Yard as a navy engineering cadet from February, 1945 and was assigned to manage the production of "Kaiten," a human torpedo. So I know "Kaiten" is a single seated vessel but could have two pilots when it was demanded. At the earlier stage of its development, it was two seaters but I do not think such a big one was not used in actual fighting. Commander Hashimoto was summoned up to the military court of the captain of the sinking USS Indianapolis as a witness of prosecutor right after the surrender of Japan. At that time, the interrogation on him was made separately from the military court. He stated that I-type submarine can carry two sets of Kaiten (Type 300 boat six units.) From this statement of him it would be probable that both Mizui and Nakai charged riding on the same vessel.
Meanwhile, just before the start of Pacific War, five small two-crew submarine boats attacked the Pearl Harbor and nine of ten crews in total were killed without getting results. Ensign Kazuo Sakamaki was captured and became POW No.1. After the war he was sent back to Japan and worked for the Toyota Motors. After he managed the export section quite a while, he was appointed the president of Toyota Brazil. I had a chance for reading his book titled ad "POW No.1" (published in 1949.) A few days before his charge, the gyrocompass of his boat had troubles. The technicians made efforts to repair them but in vain.. He left for action riding on a troubled boat. But while he could not proceed to the target, his boat was depth-charged by USS ships. After wandering around the mouth of Pearl Harbor, his boat went aground. He was arrested as a prisoner, he wrote. I saw many times test firing of torpedo at the firing range in Kure Naval Yard. Almost none of torpedoes could go straight at their first trial. Some of them made U-turns and came back to us. The gods of torpedo at Kure Naval Yard, super veteran leaders of workers, adjusted a bit on gyrocompass. The most of them went straight at the second trials. It was really amazing. The same guide system was used for ordinary torpedoes, human torpedoes and special submarine boats. The troubles on their gyrocompass were fatal defects for them. I wrote an article about these things for a magazine. He told me that he was happy to have a printed report clarifying his failure of attack was due to troubles on the gyrocompass. To say the truth, before publicizing the article, I showed him its draft. He wished to erase a few paragraphs which I made comments on the judgment of Commander Hiroshi Hanabusa of I-23 submarine. The rights and the wrongs of captain's judgment should be discussed, I think.
About the case of Mr, Mizui, I think the same discussion should be held. Captain Hashimoto replied to the inquiries of U.S. military, "Human torpedoes were only used as emergency weapons."I could not understand why these three people had to kill themselves after August 10, 1945 just before the end of war.