The Chinese wiki says after Google:
"October 11, 1841 (October 11, 1841), Kazan, Watanabe, was in search of his mother, but he was unable to reach his mother. After his death, he signed his will [his will was signed], "Unfaithful and unfilial Noboru Watanabe." [2] One of the brightest lights in the history of modern Japan, the light of thought, suddenly faded away in the turbulent political environment. At this time, Huashan [Kazan] was only 48 years old. [1]"
[in brackets what I think was meant]
So Noboru Watanabe was indeed his real name, I'ld think...