Okamura finished ninth in the all-around at the 2019 All-Japan Junior Championships.[2] She made her international debut at the 2020 WOGA Classic and finished second in the all-around to Skye Blakely.[3] She then placed 17th in the all-around at the 2020 All-Japan Championships.[4]
2021
Okamura became age-eligible for senior international competitions in 2021. She finished 15th in the all-around at the 2021 All-Japan Championships and 13th at the NHK Trophy.[5][6] She qualified for the balance beam final at the All-Japan Event Championships and placed fourth.[7] She helped her club place 12th at the All-Japan Team Championships.[8]
2022
Okamura placed 13th in the all-around at the All-Japan Championships and 11th at the NHK Trophy.[9][10] At the All-Japan Event Championships, she repeated her fourth-place finish on the balance beam.[11] She had the second-highest all-around score behind Shoko Miyata at the All-Japan Team Championships and helped her club finish 11th.[12]
2023
Okamura made her senior international debut at the Cottbus World Cup and won the gold medal on the balance beam.[13] At the All-Japan Championships, she finished seventh in the all-around,[14] and she finished also finished seventh at the NHK Trophy.[15] She finished sixth on the floor exercise at the All-Japan Event Championships.[16]
At the 2022 Asian Games, held in 2023 due to COVID-19 concerns, Okamura led the Japanese team to a second-place finish behind China.[17] She qualified for the all-around final where she won the silver medal behind China's Zuo Tong.[18] She then won a gold medal in the balance beam final, the first time a Japanese gymnast won the Asian Games balance beam title.[19] She also placed eighth on uneven bars and fourth on floor exercise.[20] At the All-Japan Team Championships, she had the second-highest score on the balance beam behind Urara Ashikawa and helped her club place tenth.[21]
2024
Okamura began the 2024 season at the Cairo World Cup where she won a gold medal on the floor exercise and a bronze medal on the balance beam.[22] She finished fourth in the all-around at the All-Japan Championships.[23] She then won the bronze medal in the all-around at the NHK Trophy and was selected for the Japanese Olympic team alongside Shoko Miyata, Rina Kishi, Haruka Nakamura, and Kohane Ushioku.[24]
^"体操の岡村選手「力出し切れた」 アジア大会金メダル 四日市市長に喜び報告" [Gymnast Okamura "I gave it my all" Asian Games gold medal, happy report to Mayor Yokkaichi]. Ise Shimbun. 9 October 2023. Retrieved 19 May 2024.
^"パリ五輪出場目指す体操・岡村真選手 私立暁高校の卒業式に出席「自分の演技を世界に見せられるように」" [Mana Okamura, a gymnast aiming to participate in the Paris Olympics, attends the graduation ceremony of Akatsuki Private High School, "I want to be able to show my performance to the world"]. Tōkai Television Broadcasting (in Japanese). 1 March 2024. Retrieved 19 May 2024.
