Sachi Umino is a character from the anime series 'Kakkou no Iinazuke' (A Couple of Cuckoos). She is the younger sister of the series' protagonist, Nagi Umino. Sachi is a bright and lively high school student who deeply cares for her brother. Her strong-willed nature often leads her to express her opinions bluntly, but her intentions are always in the best interest of her loved ones. As the story unfolds, Sachi becomes more involved in the complex relationships and situations surrounding Nagi, adding depth and warmth to the narrative.