Satsuki Tsuchida is the younger sister of Naozumi Tsuchida, a teacher at Hanamaru Kindergarten. Driven by a notable brother complex, she visits the kindergarten to check on her brother's well-being after he moved away from home. She shows deep concern for Naozumi's life and actively seeks his acknowledgment. Satsuki reacts with jealousy when Naozumi interacts closely with fellow teacher Nanako Yamamoto, reflecting possessive tendencies regarding his attention.

As a high school student, Satsuki demonstrates maturity in managing household responsibilities. She frequently criticizes Naozumi for his untidiness and late-night gaming habits. Despite her frustrations with his lifestyle, she cares for him deeply and misses their previous family life together. Her exceptional culinary skills are frequently highlighted. Satsuki has black hair reaching chest length and blue eyes.