At the 2012 World Karate Championships held in Paris, France, Kiyuna won one of the bronze medals in the men's individual kata event.

[5] The following year, he represented Japan at the 2013 World Games in Cali, Colombia and he won the bronze medal in the men's kata event.

[6] In 2014, at the World Karate Championships held in Bremen, Germany, Kiyuna won the gold medal in the men's individual kata event.

[21] A few months after the Olympics, he won the gold medal in the men's kata event at the 2021 World Karate Championships held in Dubai, United Arab Emirates.

At the gold medal ceremony for kata at the Tokyo 2020 Olympics, Kiyuna paid tribute to his mother's support by carrying a framed picture of her during the proceedings.