Midori Koshimizu is a minor character in the story. She is the older sister of Kanae Sumida, a classmate of the protagonist Takaki Tono. Midori is eight years older than Kanae. While she appears in the original animated film without a name, the live-action adaptation gives her the name Midori Koshimizu. She attended a university in Shizuoka and obtained her driving license at the age of nineteen. Her role in the narrative is limited to her relationship with Kanae, as she is not directly involved in the central storyline. There is no detailed exploration of her personality, motivations, or development within the available material.