Secret Japanese Papers Uncovered for Trials By United Press Several secret documents which most Japanese government officials thought had been destroyed will be introduced as evidence against former Premier Hideki Tojo and 25 other defendants who go on trial June 3 before the International Military Tribunal, it was learned yesterday. Exact nature of this material was not revealed, but it was learned that most of the defendants, as well as possible witnesses, have been surprised by the prosecution’s knowledge of certain information which came from secret Japanese papers now in American possession. It was reported that Saburo Kurusu, Japan’s special peace envoy to Washington at the time of the Peral Harbor attack, supplied the prosecution with much valuable information. Kurusu is slated to be a witness during the trials. Dr. Ichiro Kiyose, chief Japanese defense counsel who led an unsuccessful effort to have the indictment thrown out, also promises to have a few surprises