Reiko Katakura (片倉 鈴子 Katakura Reiko), better known as Nee-chan (or "Sis" in the English version), is the daughter of Misako Katakura, the niece of Miyako Sakashista, the older sister of Kippei Katakura and Satsuki Katakura and the cousin of Yuzuyu Sakashista.
Reiko is a strong-willed, bold and controlling woman that everyone in the family follows her orders. Although in truth, she is just trying to do what she thinks is best for them and she is especially controlling towards Kippei Katakura and was the one who ordered that he take care of Yuzuyu Sakashista.
- Misako Katakura (Mother)
- Kippei Katakura (Younger Brother)
- Satsuki Katakura (Youngest Brother)
- Miyako Sakashista (Aunt)
- Yuzuyu Sakashista (Cousin)
- The name Reiko means "bell" (鈴) (rei) and "child" (子) (ko).
- Later in the series, Reiko's secret is that she cannot have any children, in which she reveals it to Kippei Katakura.
- Reiko hires detectives/officers Misaki and Kouji to help her track down Miyako Sakashista (Yuzuyu's biological mother).
- In "Bye Bye Yellow Hat" (Episode 6), Reiko works as a cosmetologist (the study and application of beauty treatment. Branches of specialty include hairstyling, skin care, cosmetics, manicures/pedicures, non-permanent hair removal such as waxing and sugaring, and permanent hair removal processes such as electrology and intense pulsed light).
- She is a cosmetologist and everyone in Kippei's family follows her orders. She is known for her stylish outfits and nails.
- Reiko is an expert in fashion who takes great pride in her appearance.
- Kippei Katakura calls Reiko "Sis".