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 2017 CS Autumn Classic International. She placed fourth at both of her Grand Prix assignments, 2017 Cup of China and 2017 Internationaux de France. After a fifth-place finish at the 2017-18 Japan Figure Skating Championships she was assigned to the 2018 Four Continents Championships. At the championships, she was third in the short program behind countrywomen Satoko Miyahara and Kaori Sakamoto. After a second-place finish in the free skate, and mistakes from Miyahara, Mihara rose to second place overall. 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. Poor health forced Mihara to withdraw from both of her Grand Prix assignments, the 2019 Skate Canada International and 2019 Cup of China. "GP: Grand Prix; CS: Challenger Series; JGP: Junior Grand Prix"  "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."