My grandfather was Matsujiro Morikawa (b. 1877 in Ise City, Mieken, Japan and d. 1926 in Sacramento, California). His parents were Yasuke Nagata and Mino Morikawa. We know that Japanese culture provides options for parents to give either surname to a child, e.g., if the mother has no brothers they might opt to give the children the mother's surname so that her family line continues. We do not know why our grandfather was given his mother's surname.
Does your family have any connection to Ise City or Mieken?
I would delighted to hear from you.
Joe Barrett
abou505@aol.com