She medaled silver at the 2020 Winter Youth Olympics in the girls' halfpipe event and gold at the 2021 FIS Snowboarding Junior World Championships in the women's halfpipe event.

Kaji was born on 24 August 2004 in Uozu, Toyama Prefecture.

[3][4] Kaji represented Japan at the 2020 Winter Youth Olympics in the girls' halfpipe event, where she ranked second throughout, medaling silver with a score of 85.33.

[5][6][7] Kaji participated in the 2021 FIS Snowboarding Junior World Championships where she medaled gold in the women's halfpipe event.

[8] Kaji is sponsored by Roxy, a women's clothing line by Quiksilver.