[7] Sun speaks English, French, and Mandarin Chinese fluently; she expressed interest in learning Korean and Japanese.

[citation needed] Sun represented Switzerland as a junior, finishing runner-up with Violet Apisah in the 2018 Australian Open girls' doubles.

[16] She made her WTA Tour main-draw debut at the Morocco Open two days later, where she received a wildcard into the singles draw.

[17] Sun made her Grand Slam debut at the Australian Open after qualifying[18][19] but was beaten in the first round by Elisabetta Cocciaretto.

[22] In April, Sun played under the New Zealand flag for the first time as part of the team for the 2024 Billie Jean King Cup.

[citation needed] She qualified for the 2024 Wimbledon Championships making her debut at this major and upset eighth seed Zheng Qinwen in the first round.

[27] She equalled the feat of reaching the fourth round at the All England Club as the first New Zealand female player in the Open Era, and second after Dame Ruia Morrison in 1957 and 1959.

64, she qualified for the Cincinnati Open making her debut at this WTA 1000, and defeated Linda Nosková in the first round,[34] before losing to 15th seed Marta Kostyuk.

[44] Sun withdrew from her next scheduled tournament, the Hong Kong Tennis Open, and announced she was bringing an end to her 2024 season.