[5][6] She became a part of the Japanese women's team that won a silver medal at the 2018 World Team Table Tennis Championships in Halmstad, Sweden.

[7] In September 2019, Nagasaki won both the girls' singles and doubles (with Miyuu Kihara) at the Asian Junior and Cadet Championships.

[8] Nagasaki continued to win both the girls' singles and doubles at the 2019 World Junior Championships.

She was the first non-Chinese girl to win the singles in the tournament's 17-year history.

[9] Two weeks later, she and Kihara captured the women's doubles title at the 2019 ITTF World Tour Grand Finals.