Sasaki was born on February 8, 1988, in Akita, the capital of Akita Prefecture, into a low-income family. Her father died in a car accident when Nozomi was a teenager, and the family was on the brink of poverty. All responsibility for raising the children, and Nozomi has two older brothers, fell on the shoulders of the girl's mother.

But at that time, although her mother tried very hard, the family was still poor, and at 14 Sasaki Nozomi got a job, practically dropping out of school. She never finished her education and still has difficulty reading complex texts, which causes problems during television filming when Nozomi cannot correctly read the director's cue on the monitor. It is believed that this time was the beginning of her modeling career, but that is not quite true. She got a job at a shop attached to a studio opposite the railway station of Akita Station and was formally considered a model, but the work of a provincial model is absolutely unlike the work of a high-class professional model. She more often had to work as a salesperson and communicate with customers, which she did very reluctantly, causing dissatisfaction both among the customers themselves and the shop. Therefore, when in May 2005 the magazine Weekly Young Jump organized the Gyarucon 2005 beauty contest in Akita to find new models, the manager literally forced Sasaki Nozomi to take part in it. She reluctantly agreed, and this decision instantly turned her life around, as she won the grand prix of the contest, and with it future success. In April 2017, she married comedian and TV host Ken Watabe. On September 13, 2018, she gave birth to a son.