Sadako Maki, maternal great-aunt to a seriously ill boy named Sho, resides in a Koganei house in western Tokyo inherited from Sho’s mother. With Sho’s parents occupied by work, he moves in to rest before a critical heart operation. Sadako understands their constraints but wishes they could support Sho more directly. She welcomes him without burden, valuing his presence.

Employing a maid named Haru, Sadako carries family knowledge of the Borrowers’ existence. Her father acknowledged them by building a functional dollhouse for their use, though Sadako has never encountered them and remains uncertain if they inhabit the home.

Calm and perceptive, Sadako contrasts Haru’s excitable suspicion. When Haru calls pest control to prove the Borrowers are real, Sadako intervenes—sending the exterminators away upon her return, asserting authority with composure. Initially skeptical due to absent evidence, she later discovers herbs inside a sealed teapot, an inexplicable event that hints at her silent acknowledgment of the Borrowers’ potential reality.

Her guardianship of Sho continues after the Borrowers depart. Sho undergoes successful heart surgery and returns to visit Sadako’s house roughly one year later.