Midori Yoshinaga teaches the Sunflower class at Futaba Kindergarten. Initially known by her maiden name, her life changes significantly upon marrying Junichi Ishizaka on July 7, 2000, leading her to adopt the surname Ishizaka. This marriage prompts their move to a larger apartment, abandoning her previous residence that once hosted the Kasukabe Defense Organization; the group later seeks her new home.

She maintains a fierce rivalry with fellow teacher Ume Matsuzaka, frequently clashing over topics like physical appearance and chest size. Despite their arguments, she shows care for Matsuzaka, occasionally looking out for her well-being. Her personality includes a notable self-absorption, often considering herself exceptionally beautiful.

Following her marriage to Junichi, she gives birth to a daughter, Momo Ishizaka, with Nushiyo Ooya and Shinnosuke Nohara assisting during the delivery. Motherhood adds a new facet to her character, though she continues her teaching duties.

Her film appearances, including "Crayon Shin-chan: Buriburi Ōkoku no Hihō," "Action Kamen vs Haigure Maô," "Ankoku Tamatama Daitsuiseki," and "Arashi o Yobu Appare! Sengoku Daikassen," consistently feature her professional role and interactions within the kindergarten environment.