The Housekeeper is a practical-minded single mother working for the Akebono Housekeeping Agency. Having grown up with an absent mother and becoming pregnant in high school, she learned to manage a household out of necessity. She is diligent and known for handling difficult clients, approaching her new assignment at a mathematician's cottage with professional resolve.

The Professor is a 64-year-old mathematician who specializes in number theory. Following a car crash in 1975, his short-term memory lasts exactly eighty minutes, forcing him to pin paper notes to his suit jacket to remember daily facts. He views the world through the pure logic of mathematics and often speaks in equations to handle social interactions comfortably.

Root is the ten-year-old son of the Housekeeper. He earns the nickname "Root" from the Professor because the flat top of his head resembles a square root symbol. Accustomed to spending time alone while his mother works long shifts, he is highly independent and responsible for his age.

The Widow is the Professor's sister-in-law, living in the main house on the south side of the property. She manages the estate left by her late husband, living off the rent from apartment buildings built over the old family factory. She establishes firm boundaries, forbidding the hired help from bothering her in the main house.

The Housekeeper's Mother is a deceased woman who worked long shifts at a wedding reception hall. She became furious when her daughter became pregnant in high school, leading to an extended separation between them that ended shortly before her death.

The Professor's Brother was a wealthy businessman who successfully expanded their parents' textile factory. Being significantly older than the Professor, he acted as a provider and funded the Professor's university studies before passing away.

Root's Father is a former college student who dated the Housekeeper while she was in high school. He refused to take responsibility when she became pregnant, forcing her to leave home and secure employment to support their child.

The Director of the Akebono Housekeeping Agency assigns workers to various clients around the city. The Director recognizes the Housekeeper's ability to handle difficult assignments and relies on her to manage the high turnover at the Professor's cottage.