Midori Imai anchors a quintet of friends forged in Kaminoyama High School's animation club. Their shared creation of an original short film for the school festival culminated in a pact, sealed with doughnuts, to chase professional animation careers in Tokyo—a promise fueling her journey. Post-graduation, she enters university while actively pursuing her ambition to become a versatile scriptwriter capable of crafting emotionally resonant stories across genres. Kind, perceptive, and fervently dedicated to learning, Midori is the group's youngest member, nurturing large dreams often inspired by her friends while consistently offering them support. Her distinct appearance features black-purple hair in a high side ponytail secured by a white hair tie, grey-purple eyes, and a preference for vibrant clothing: a black-and-white pinstripe dress with a brown belt, mustard blazer, and magenta star-patterned tights.

Her professional path begins assisting friend Aoi Miyamori, a production assistant at Musashino Animation, with extensive diesel train engine research for *Exodus!*. The resulting thorough document earns her the studio nickname "Diesel-san." Recognizing her research prowess, Musashino Animation hires her part-time as a setting instructor, conducting detailed research to enhance story immersion. She later transitions into script ordering assistance under the mentorship of scenario writer Maitake Shimeji, who guides her writing development. A challenge arises when new production assistant Daisuke Hiraoka suggests Midori receives preferential treatment due to her gender. This motivates her to prove her value through diligent work and substantiated contributions, strengthening her resolve to succeed on merit. Her commitment includes personal sacrifices like all-nighters reading Fyodor Dostoevsky; imagery from his work later appears as a jet decal in an anime opening.

Residing in the same apartment complex as Aoi, Midori accompanies Aoi's older sister Kaori on Tokyo tours when Kaori visits, dissatisfied with her career. During this, Kaori shares insights about the vulnerabilities of people deeply committed to their work, which Midori absorbs thoughtfully. Midori recognizes these activities inadvertently benefit her own growth more than Kaori's, prompting her to suggest Kaori take initiative before returning home. Four years later, depicted in the sequel film, Midori continues at Musashino Animation. She contributes creatively to the film *Aerial Amphibious Assault Ship SIVA (SIVA)*, providing ideas that help Maitake overcome writer's block. She also joins her four friends in an animation class for children led by former animator Shigeru Sugie, reigniting their shared passion and reinforcing their dedication to *SIVA*.

Throughout, Midori evolves from an aspiring student into a proactive industry contributor, overcoming challenges through persistent effort and leveraging her research expertise. Her foundational friendships provide mutual support as they collectively pursue their high school promise.