Career beginnings

Shinohara made his professional debut against Tasuku Kido at HOOST CUP KINGS WEST on November 16, 2014. He won the fight by a first-round knockout.^[6] Shinohara faced Shinichiro Kawasaki a month later, at DEEP KICK 23 on December 21, 2014. He won the fight by unanimous decision. 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.^[7]

His spotless professional record and the Koshien tournament win, led to Shihonara being signed by K-1. He made his debut with the organization against Yuki Koge at K-1 World GP 2016 -60kg Japan Tournament on April 24, 2016. He won the fight by a second-round knockout, stopping Koge with a flurry of punches at the 1:15 minute mark.^[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. Matsushita won the fight by a second-round knockout, handing Shinohara both his first professional loss and his first stoppage loss.^[9] Shinohara next faced Tatsuya Mineyama at K-1 World GP 2016 Featherweight Championship Tournament on November 3, 2016. He won the fight by unanimous decision, with all three judges scoring the bout 30–27 in his favor.^[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. He was booked to face Jun Nakazawa in the tournament semifinals, which were held at Krush.73 on February 18, 2017. He lost the fight by a second-round knockout. Shinohara was first knocked down with a left hook midway through the round, and was knocked out with a second left hook soon afterwards.^[12]

Title run

Shinohara faced Kensei Kondo Krush.79 ～in NAGOYA～ on August 20, 2017. The two previously fought in the finals of the 2015 K-1 Koshien tournament, with Shinohara winning by a third-round knockout. He was proved to be the better fighter in their second meeting as well, winning the fight by a second-round knockout.^[13]

Shinohara faced FUMIYA at KHAOS.4 on October 14, 2017, representing Kansai in a "Kantō vs Kansai 6 versus 6" themed event.^[14] He won the fight by a third-round knockout, stopping FUMIYA with a right cross a minute into the round. Shinohara was furthermore awarded the MVP prize as well, as the best fighter of the event.^[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 fight by unanimous decision, with all three judges awarding him a 30–27 scorecard.^[16]

Shinohara was booked to face FUMIYA at Krush.88 on May 17, 2018. The pair had fought just seven months prior, with Shinohara winning by a third-round knockout. 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.^[17]

Shinohara vs. Nakazawa

At a press conference held by Krush on June 28, 2018, it was announced that Shinohara would challenge the reigning Krush Super Lightweight champion Jun Nakazawa, in what was Nakazawa's second title defense. The bout was scheduled as the co-main event of Krush.91, which was held on August 5, 2018.^[18] He won the closely contested fight by split decision. Two of the judges scored the fight 30–29 in his favor, while the third judge scored the fight 30–29 for Nakazawa.^[19] Shinohara stated his desire to move down to lightweight (62.5 kg) in his post-fight interview, as he felt at a weight disadvantage at super lightweight.^[20]

K-1 Lightweight Grand Prix

On October 20, 2018, K-1 announced they would hold a Lightweight Grand Prix at K-1 World GP 2018: K-1 Lightweight World's Strongest Tournament on December 8, 2018. Shinohara was booked to face the reigning Krush Lightweight champion Kongnapa Weerasakreck in the tournament quarterfinals.^[21] Shinohara knocked Kongnapa with a left hook early in the first round, and although he was able to beat the ten count, Shinohara knocked down him a second time with another left hook soon after. These two knockdowns awarded Shinohara an automatic technical knockout victory under the K-1 tournament rules. He needed just 25 seconds to advance to the next round.^[22]

Shinohara advanced to the tournament semifinals, where he faced Kenta Hayashi. Hayashi first knocked Shinohara down with a right hook, before stopping him with a right cross at the 2:31 minute mark of the first-round.^[23] Ten days later, on December 18, Shinohara vacated the Krush super lightweight title.^[24]