Akamatsu began high jumping as early as 2013, when he finished 3rd at the Japanese high school championships representing Kano High School [ja].[6] Until 2022, he had only jumped twice outside of Japan — once at the Taiwan Athletics Open Meeting in 2016, and once at the 2019 China–Japan–Korea Friendship Athletic Meeting in South Korea where he finished 3rd.[7][8]
After winning his first national title at the 2023 Japanese Indoor Championships, Akamatsu competed at the 2023 Asian Indoor Athletics Championships, where he won the gold medal.[11] He defended his title at the 2023 Japanese Athletics Championships, earning him qualification to represent Japan at the Asian Championships where he finished 5th. Following that competition, he set his personal best of 2.30 metres at the Twilight Games in Tokyo, making him the 6th-highest Japanese jumper in history.[3]
At the 2023 World Championships, Akamatsu qualified for his first global final and finished 8th.[12][13][14] He didn't jump as high in the finals as he did in the preliminary round, claiming he was overworked.[15] He ended his season at the 2023 Asian Games in Hangzhou, finishing tied for 2nd in qualification and 6th in the final.[16]
