During the 2013–14 season, Mihara debuted on the ISU Junior Grand Prix circuit, placing fifth in Minsk, Belarus. After winning the Japanese national silver medal on the junior level, she finished her season by placing twelfth on the senior level at the Japan Championships.
2014–2015 season
Mihara started her season by placing sixth at her JGP event in Ljubljana, Slovenia. She then placed seventh at the Japan Junior Championships and ninth at the Japan Championships.
In September, Mihara competed at her first Challenger Series competition, the 2016 CS Nebelhorn Trophy. Ranked second in the short program and first in the free skate, she won the gold medal ahead of Russia's Elizaveta Tuktamysheva. Her Grand Prix debut came the following month at the 2016 Skate America. She was awarded the bronze medal, behind American skaters Ashley Wagner and Mariah Bell, after placing second in the short and third in the free. She finished fourth at her next Grand Prix assignment, the 2016 Cup of China. In December 2016, Mihara took bronze at the Japan Championships, having ranked fifth in the short and second in the free. In February 2017, she placed fourth in the short and first in the free at the Four Continents Championships in Gangneung, South Korea, outscoring Canada's Gabrielle Daleman by 3.94 points for the gold medal. In March 2017, Mihara competed at the 2017 World Championships in Helsinki, Finland. Ranked fifteenth in the short program after doubling and falling on a planned triple flip, Mihara ranked fourth in the free skate and climbed to fifth overall. In April, she competed as part of Team Japan at the 2017 World Team Trophy. She achieved a personal best of 72.10 points in the short program and then scored a Japanese national record of 146.17 points in the free skate. She finished second behind Medvedeva and 0.83 ahead of compatriot Wakaba Higuchi while Team Japan won the gold medal.
Mihara won silver at the 2018 CS Nebelhorn Trophy. On the Grand Prix, she first competed at the 2018 NHK Trophy, the most hotly-contested ladies' event on the Grand Prix that year. She was third in the short program, but dropped to fourth in the free skate and overall despite making only one error, a jump underrotation. She then narrowly placed second at the 2018 Internationaux de France, slightly behind compatriot Rika Kihira. Mihara said she was unsatisfied with her free skate in France, but that "overall, it was a good experience for me and I will continue to practice to gain more confidence." At the 2018 Japan Championships, Mihara placed third in both programs, finishing fourth overall. She was again assigned to the Japanese team for the Four Continents Championships. Competing at Four Continents, she underrotated her opening combination jump to place eighth in the short program. She described this as an error she would not normally make even in practice. Mihara then placed second in the free skate, winning the bronze medal overall, her third consecutive Four Continents podium finish. Mihara concluded her season at the 2019 Winter Universiade, where she won the ladies singles' title.
Small medals for short and free programs awarded only at ISU Championships. At team events, medals are awarded for team results only. T – team result. P – personal/individual result. Bolded scores reflect a personal best.
