Miyamoto is a native of San Francisco and a graduate of Lowell High School.
[1] His father was Philip Miyamoto, an appellate judge for the state of California of Japanese descent.
[2] In March 2020, at the beginning of the COVID-19 pandemic in San Francisco, Miyamoto suspended county jail visits and programs to preemptively stop the spread of COVID-19.
[8] Miyamoto's family was interned during WWII at Heart Mountain Relocation Center.
[2] Miyamoto said that films like The Choirboys (1977) and End of Watch (2012) and television show Hill Street Blues (1981–1987) depict an accurate portrayal of law enforcement.