Miri Unasaka is a four-year-old girl with short brown hair curled inwards, bangs just above her eyebrows, and large brown-orange eyes set against pale skin. A pink hair accessory typically clips her hair on the left side. Her usual attire consists of a pink thick winter coat worn over an orange turtleneck sweatshirt, paired with light-brown shorts, black leggings, and pink shoes. Sent away by her mother, singer and prostitute Misaki Unasaka, on Christmas Eve to find her biological father, human trafficking broker and mafia boss Atsushi Hayami, Miri carried photographs to identify him. Misaki, resenting Miri due to an unplanned pregnancy and seeing her as a burden, harbored feelings unknown to the child. Miri encountered assassins Kazuki Kurusu and Rei Suwa during their mission at her father's hotel. When Kazuki impulsively claimed to be her father during a hostage situation to protect her, and following Hayami's subsequent death, the assassins took her in. Though Misaki briefly reclaimed Miri after a cancer diagnosis, her own death soon after left Miri permanently in Kazuki and Rei's care. Miri exhibits a cheerful, energetic, and trusting personality, marked by notable naivete for her age. She often fails to recognize dangers like gunfire or being held at gunpoint. Her speech is loud, reflecting her hyperactivity and struggles with volume control. Despite her mother's resentment, Miri expresses deep affection for Misaki, frequently praising her store-bought hamburg steak over Kazuki's cooking. She forms strong attachments quickly, calling Kazuki "Papa Kazuki" and Rei "Papa Rei" after Rei rescues her from police custody. Her innocence complicates the assassins' missions, such as when she inadvertently exposes details about their weapons at daycare. Her development shows gradual integration into Kazuki and Rei's lives, influencing Rei to embrace a paternal role when he retrieves her from authorities, defying his abusive past. Miri's presence challenges their lifestyles, leading them to enroll her in daycare using forged documents. Her perception of family evolves, culminating during a scavenger hunt where she identifies Kazuki and Rei as "family," reinforcing their bond. The series epilogue, set years later, shows her continuing to live with them as a teenager, reflecting their established family unit. Her name, written entirely in katakana as ミリ (Miri), is interpreted as "milli," symbolizing a one-thousandth part. This aligns with the numerical themes in Kazuki's name (containing "one") and Rei's (containing "zero"), emphasizing her small size and youth within their dynamic.