Approximately 30 years ago, the author of the present paper discovered that the funeral bronze mirror unearthed from the Takamatsuzuka Tumulus of Japan and called mirror decorated with marine mammals and grape vines is identical in size, shape and decoration with that from the Dugu Sizhen tomb in the eastern suburbs of the capital Chang’an of Tang China, and that the two objects are mirrors cast in the same mold in China. As Dugu Sizhen was buried in AD 698 according to his epitaph, it can be inferred that the mirror under discussion was taken to Japan by the seventh Japanese delegation to Tang China that entered the Tang Empire in 702 and returned to Japan in 704. Soon the mirror passed into the hand of Prince Osakabe for he was Premier of Japan. According to literal records, Prince Osakabe died in May 705, which provides an important clue for clarifying the date and tomb-owner of the Takamatsuzuka Tumulus. Up to now, the author has held the above view firmly and without any change. In the present paper, he reaffirms this understanding and criticizes someone’s so-called dissenting argument. Approximately 30 years ago, the author of the present paper discovered that the funeral bronze mirror unearthed from the Takamatsuzuka Tumulus of Japan and called mirror decorated with marine mammals and grape vines is identical in size, shape and decoration with that from the Dugu Sizhen tomb in the eastern suburbs of the capital Chang’an of Tang China, and that the two objects are mirrors cast in the same mold in China. As Dugu Sizhen was buried in AD 698 according to his epitaph, it can be inferred that the mirror under discussion was taken to Japan by the seventh Japanese delegation to Tang China that entered the Tang Empire in 702 and returned to Japan in 704. Soon the mirror passed into the hand of Prince Osakabe for he was Premier of Japan. According to literal records, Prince Osakabe died in May 705, which provides an important clue for clarifying the date and tomb-owner of the Takamatsuzuka Tumulus. Up to now, the author has held the above view firmly and without any change. I n the present paper, he reaffirms this understanding and criticizes someone’s so-called dissenting argument.