It is unclear if just Keiko's mother lived in Kumamoto or if her father lived there as well. If it was just her mother then this may indicate that her parents were divorced, as it was later established that both of her parents were alive later in the series.
The script and the Star Trek Encyclopedia (3rd ed., p. 254) gave the spelling of this city as "Kumomoto". This spelling was corrected for the fourth edition (vol. 1, p. 447). In the script pronunciation guide, Kumomoto was pronounced as "koo-moh-MUH-toh".