But it is said that there was a problem on protection at the part of castle, which Hideyoshi himself worried about, (Nobushige (Yukimura) SANADA built a fort, which was called Sanadamaru, on that weak point for later Siege of Osaka to reinforce protection of Osaka Castle and plagued TOKUGAWA troops.
しかし城の一部に防御上の問題が有り、秀吉自身もそこを気にしていたと言われている（のちの大坂の役で真田信繁（幸村）は、防御の弱さを指摘されていた箇所に真田丸と呼ばれる砦を築き、大坂城の防御を大幅に強し、徳川勢を大いに苦しめた）。