Zakuro Mitsukai is the nine-year-old younger sister of Dokuro Mitsukai, appearing paradoxically more physically mature than her older sister in height and bust size. As an angel dispatched from the future, she exhibits a calm, soft-spoken, and polite demeanor, frequently using the formal honorific "-san," creating a distinct contrast to Dokuro's impulsive nature. Her attire consists of a naval officer-style uniform and an unexplained eyepatch covering her left eye.

Initially arriving alongside other future angels, Zakuro receives assignments to retrieve Dokuro and monitor Sakura Kusakabe pending decisions about his fate. She wields Eckilsax, her primary weapon—a magically enhanced wet towel capable of splitting into multiple sections for close combat or stretching to bind opponents. Zakuro demonstrates battle proficiency with an elegant fighting style.

Later, Zakuro relocates to live with Sakura and Dokuro, signaling a shift from her initial hostility. Her interactions with Sakura reveal ambivalence: she occasionally suggests Dokuro should kill him to resolve conflicts, though typically offering apologies afterward. Simultaneously, she displays underlying affection toward him, contributing to tension with Dokuro. Zakuro's physical development consistently becomes a point of jealousy for her older sister.