San Hōjō is the mother of Shusaku Hojo and becomes Suzu's mother-in-law when Suzu marries into the Hojo family in Kure. She possesses a gentle and compassionate personality, treating Suzu with consistent kindness and respect. This treatment contrasts with the often servant-like role expected of daughters-in-law in arranged marriages. A leg injury restricts San's mobility, limiting her ability to perform domestic chores. This physical condition necessitates additional household help and partly influences the family's acceptance of Suzu as Shusaku's bride.

Throughout the war, San maintains a calm and composed demeanor despite escalating hardships. She temporarily loses her husband, Entarō Hojo, an aircraft engine engineer at the Hiro Naval Arsenal, following air raids. He is later found injured but safe at Kure Naval Hospital. San endures the death of her granddaughter Harumi, killed in a bomb explosion, and supports her family through this grief.

In the extended version of the film, San participates in efforts to rebuild daily life after the war. She remains present as Suzu grapples with depression following multiple losses, including the death of her own family in the Hiroshima bombing and the amputation of her right hand. San serves as a stabilizing presence, embodying resilience as the family adopts an orphaned girl and moves forward in postwar Japan.