[4][5] Shinohara made his professional debut against Tasuku Kido at HOOST CUP KINGS WEST on November 16, 2014.
After notching his first two professional wins, Shinohara returned to amateur competition, in order to take part in the K-1 Koshien 2015 Tournament.
He won the Koshien title with a third-round knockout of Kensei Kondo at K-1 World GP 2015 The Championship on November 21, 2015.
[8] Shinohara next made his debut with K-1's sister organization Krush, as he was booked to face Daiki Matsushita at Krush.67 on July 18, 2016.
[9] Shinohara next faced Tatsuya Mineyama at K-1 World GP 2016 Featherweight Championship Tournament on November 3, 2016.
[10][11] After successfully rebounding from his loss to Matsushita, Shinohara took part in the Krush Super Lightweight tournament, held to crown the new champion as Hideaki Yamazaki was stripped of the title due to injuries.
[15] Following a split decision victory against Hayato Suzuki at K-1 WORLD GP 2017 JAPAN ～SURVIVAL WARS 2017～ on December 27, 2017, Shinohara returned to Krush to face Takaki Hosogoe at Krush.86 on March 11, 2018.
He won the rematch in the same manner, forcing a referee stoppage at the 1:50 minute mark, after having knocked FUMIYA down twice with left hooks.
Shinohara was booked to face the reigning Krush Lightweight champion Kongnapa Weerasakreck in the tournament quarterfinals.
[24] Shinohara faced the 2018 K-1 Lightweight Grand Prix finalist Fumiya Osawa at K-1 World GP 2019: K'FESTA 2 on March 10, 2019.
[27] Shinohara was rewarded with this two-fight winning streak with the chance to challenge the reigning Krush Lightweight champion Kongnapa Weerasakreck, in the main event of Krush.113 on June 28, 2020.
[30] Shinohara was expected to face the former Krush Super Featherweight champion Yuma Saikyo at K-1: K’Festa 4 on January 24, 2021.
[31] The entire event was later postponed as the Japanese prime minister Yoshihide Suga declared a state of emergency for Tokyo, due to the COVID-19 pandemic.
[38][39] Shinohara faced the reigning Krush Lightweight champion Shuji Kawarada at K-1 World GP 2022 Japan on February 27, 2022.
[45] Shinohara faced the two-time K-1 Koshien super lightweight tournament winner Ryuka at K-1 World GP 2023 on July 17, 2023.
[47] Shinohara faced the two-time Krush Super Featherweight title challenger Tatsuya Oiwa at K-1 ReBIRTH 2 on December 9, 2023.