Midori Yoshinaga teaches the Sunflower class at Futaba Kindergarten. She married Junichi Ishizaka on July 7, 2000, adopting the surname Ishizaka. This marriage prompted a move to a larger apartment, leaving her former residence where the Kasukabe Defense Organization held meetings; the group eventually tracked her down at her new home.

She shares a competitive and frequently argumentative dynamic with colleague Ume Matsuzaka, their clashes often centering on physical appearance and chest size. Despite their rivalry, she sometimes shows concern for Matsuzaka's welfare. A marked trait is her self-absorption, frequently viewing herself as exceptionally beautiful.

Following her marriage to Junichi Ishizaka, she gave birth to a daughter named Momo Ishizaka. Nushiyo Ooya and Shinnosuke Nohara assisted during the delivery. Becoming a mother added a new facet to her life, yet she maintained her teaching position at Futaba Kindergarten.

Her role as a kindergarten teacher features in multiple theatrical films: "Crayon Shin-chan: Buriburi Ōkoku no Hihō," "Action Kamen vs Haigure Maô," "Ankoku Tamatama Daitsuiseki," and "Arashi o Yobu Appare! Sengoku Daikassen." Within "Action Kamen vs Haigure Maô," she participates directly in the plot, fleeing with the Nohara family and others to a laboratory for safety after confronting threats from aliens.