Mikage Tsumura supervises Sai Nanohana's writing work throughout the series, maintaining professionalism despite Sai's past unrequited romantic feelings; Mikage is married to Mick.

When Jiyu Nanohana suffers memory loss after trauma, Mikage steps into the role of a surrogate mother figure at Sai's request, living with the Nanohana family to provide stability. This forms a temporary family unit including Freesia Yagyu, built upon hidden truths and mutual secrecy.

Mikage actively works to restore Jiyu's memories and resolve her identity crisis. Alongside Sai, she guides Jiyu to confront her responsibilities and ultimately embrace her destiny as Yagyu Jubei's successor. Her involvement contributes significantly to Jiyu's emotional recovery and decision to resume her duties.

The narrative focuses solely on Mikage's interactions with the central characters, tying her development to her professional obligations and temporary supportive familial role during Jiyu's confusion.