Takeo Yoshikawa Early career . A 1933 graduate of the Imperial Japanese Naval Academy at Etajima ( graduating at the top of his class ) , Yoshikawa served briefly at sea aboard the armored cruiser " Asama " as well as submarine s and had begun training as a naval pilot near the end of 1934 when a severe stomach ailment prevented him from completing his training . He was subsequently discharged from the Imperial Japanese Navy in 1936 . As a result , he briefly contemplated suicide . A year later he began a career in Naval intelligence , being assigned to Navy Headquarters in Tokyo . He became an expert in the U . S . Navy , perusing through every source he could possibly get his hands on . While on intelligence duty he intercepted a shortwave radio message in plain English that 17 troop transports were en route to England , having cleared the port of Freetown . He passed this information to the German Embassy , and many of the ships were destroyed as a result . Yoshikawa subsequently received a personal letter of thanks from Adolf Hitler . In 1940 he became a junior diplomat after passing the Foreign Ministry English examinations . A spy in Hawaii . Because of his expertise on the U . S . Navy , Yoshikawa was sent to Hawaii under the cover of being a vice - consul named Tadashi Morimura ( 森村 正 " Morimura Tadashi " ) , arriving on March 27 , 1941 with Nagao Kita ( 長尾 北 " Kita Nagao " ) , the new Japanese Consul - General aboard the liner " Nitta Maru " . He rented a second story apartment that overlooked Pearl Harbor and would often wander around the island of Oahu taking notes on Fleet movements , and security measures . He rented small planes at John Rodgers Airport and flew around observing U . S . installations as well as diving under the harbor using a hollow reed as a breathing device . He also gathered information by taking the Navy ' s own harbor tugboat and listening to local gossip . He worked closely with German Abwehr agent Bernard Kuehn , as well as another former Etajima graduate , Kohichi Seki ( 関 宏一 " Seki Kō ' ichi " ) , an untrained spy who served as the consulate ' s treasurer . According to Yoshikawa , although some 160 , 000 persons of Japanese ancestry lived in Hawaii at that time , he never made use of this resource in his espionage activities . He and Seki agreed while Hawaii should be the " easiest place " to carry out such work in view of the large Japanese population , both looked at the locals with disdain . " [ T ] hose men of influence and character who might have assisted me in my secret mission were unanimously uncooperative . . . " Although he had no knowledge of a planned attack on Pearl Harbor , Yoshikawa assumed that the intelligence would help prepare for such an eventuality and worked tirelessly to that end . His reports were transmitted by the Japanese Consulate in PURPLE code to the Foreign Ministry , which passed them on to the Navy . Although the code had been broken by American codebreakers and messages to and from Tokyo were intercepted and decrypted , communications between Tokyo and the consulate were considered low - priority because they contained so many messages that were entirely commercial in nature . However , one such message addressed to Kita ( but actually to Yoshikawa ) and sent on September 24 , 1941 should have received more attention . It divided Pearl Harbor into five distinct zones and requested that the location and number of warships be indicated on a " plot " ( i . e . , grid ) of the harbor . However due to delays caused by staff shortages and other priorities the message was not decrypted and distributed until mid - October , and then dismissed as having little consequence . But it was the reports that he sent twice a week based on this request that enabled Admiral Isoroku Yamamoto to finalize his plan for the attack . . " When he heard the " " East wind , rain . " " code phrase on the short wave radio bringing the news from Tokyo signaling an attack against America , Yoshikawa destroyed all evidence of his activities . When the FBI picked him up on the day of the attack there was no incriminating evidence of his espionage . Yoshikawa eventually returned to Japan in August 1942 in a diplomat prisoner exchange . It was not known for some time that he was the chief Japanese agent in Hawaii . Return to Japan and later life . Takeo Yoshikawa never received any official recognition of his services despite the fact that he continued to work for naval intelligence during the remainder of the war . When the war ended and Japan was occupied by U . S . forces he went into hiding ( disguised as a Buddhist monk ) for fear of being prosecuted for his role in the Pearl Harbor attack . He returned to his wife ( whom he married shortly after his return from the U . S . ) when the Americans left . In 1955 he opened a candy business but it failed as word spread of his role in the war . The Japanese blamed Takeo for the war ; " They even blamed me for the atomic bomb , " he declared in one interview . Penniless and jobless , he was supported by his wife for the rest of his life via her position selling insurance . " My wife alone shows me great respect , " said the old spy . " Every day she bows to me . She knows I am a man of history . " He died in a nursing home . Over the years , the mysterious spies of Pearl Harbor were always mentioned in passing in history books . While Yoshikawa contributed to the decision to intern Japanese Americans he himself distrusted the Japanese - American community who in his mind were loyal to America over Japan .