The third son Shinzaburo (then president) filed a suit seeking reversal of the "second will" which Shintaro owned, based on that: at the time of creating the "second will," Nobuo, who suffered a stroke, did not have the capacity to draw up a will while under conditions requiring nursing care; in contrast to the "first will" written with a brush on rolled paper with a registered seal, the "second will" was written with a ballpoint pen on letter paper (note that the form of paper is not a legal issue); and the seal placed on the second will was not "Ichizawa (一澤)," but "Ichizawa (一沢)" which was the registered family name of Shintaro (Tsunesaburo (the former president, then executive director), the younger brother of the late Nobuo, also made the same argument).
信三郎は、「第2の遺言書」の作成時点では既に脳梗塞のために要介護状態で書くのが困難であった事、「第1の遺言書」が巻紙に毛筆で書いて実印を捺印しているのに対して、「第2の遺言書」が便箋にボールペンで書かれていること（但し、法律上は用紙は関係ない）、捺印している印鑑が「一澤」ではなく信太郎の登記上の名字「一沢」になっていることから、当時社長だった三男・信三郎は信太郎が保有する「第2の遺言書」の無効確認を求め提訴する（故・信夫の弟で、当時専務であった元社長・恒三郎も同様の疑問を投げかけている）。