Notsugi Futago is the younger twin sister in the Futago pair, her name originating from the Japanese term "futago no tsugi," meaning "the younger twin." She refers to her older twin sister, Nosaki Futago, as "Saki," while Nosaki often remarks that Notsugi's voice is too loud and calls her "Tsugu." Notsugi identifies Bocchi Hitori as "Hito-chan."

She ties her hair in a right-sided ponytail adorned with a star-shaped hair accessory and wears her school uniform more loosely than her sister, reflecting her laid-back nature.

Notsugi shares Bocchi Hitori's middle school class and participates in a cooking group with Bocchi, Ito Kurie, Peko Onaka, and her sister Nosaki. Bocchi formally befriended Notsugi during a New Year's shrine visit, an event that occurred after Bocchi learned to distinguish between the twins and marked a step forward in their relationship.