Sachiko, Chako's relative and guardian, resides with her. She is a widow perpetually dressed in mourning attire to honor her deceased husband. A mysterious blue-haired woman is seen leaving purple roses at Sachiko's husband's grave. Sachiko displays visible shock upon spotting this woman in the audience during a cosplay competition between Chako and Ranko. The narrative leaves the blue-haired woman's identity and connection unresolved, though she later appears as a limousine driver for the rival Shin-Takarazuka Cosplay Club.

Sachiko financially sponsors the East Oizumi Cosplay Club. During an incident, Jenny Matel mistakenly enters Sachiko's bed at night while attempting to reach Athena Imai's. Unaware of Jenny's intent and identifying herself as a lonely widow, Sachiko engages in an off-screen sexual encounter with Jenny. This incident leads Jenny to develop a newfound attraction to older women.