She was the 2023 Japanese Champion in the 400 m, and won a bronze medal in the mixed 4 × 400 m relay at the 2023 Asian Championships.

Beginning as a short sprinter as early as 2014, Kuboyama won the 2018 Japanese University Championships in the 100 metres, running 11.86 into a -2.1 m/s headwind.

[1] Kuboyama switched events to the 400 metres in 2021, debuting at 54.90 and eventually finishing 4th at the 2021 Japanese Athletics Championships in 53.72.

After finishing 4th in the individual 400 m, she won a bronze medal running second leg of the mixed relay final, setting a Japanese record of 3:15.71 in the process.

The following day she also placed 4th leading off the women's 4 × 400 m.[1] [5] In April 2024, it was revealed that 2023 Asian Championships 400 m silver medallist Fairda Soliyeva of Uzbekistan failed a test for meldonium, disqualifying her and promoting Kuboyama to the bronze medal.