He competed at the 2024 Summer Olympics and won the silver medal in the 400m individual medley event.

[3][4] He swam for a club in Utsunomiya and later enrolled at Toyo University, where he received training under coach Norimasa Hirai, who also coached Olympic gold medalist Kosuke Hagino, one of Matsushita's favorite swimmers.

[7] Later that year, he competed at the 2022 FINA World Junior Swimming Championships and won silver in the 200m individual medley.

[2] The following year, he was selected for the 2023 World Aquatics Junior Swimming Championships, where he won the gold medal in the 400m individual medley while setting the championship record in the event with a time of 4:10.97.

[4][5][8] At the Olympics, Matsushita was the youngest participant in the event but reached the finals, where he won the silver medal, only behind gold medalist Léon Marchand of France.