[4] Kasahara faced his second foreign opponent, Kim So Hu, at Shoot Boxing 2017 Young Cesar in Hanayashiki act.3 on August 6, 2017.
[5] He won the fight by a first-round technical knockout, forcing Kim's corner to throw in the towel near the end of the round.
[7] Kasahara faced the WMC Japan super flyweight champion Koki Yamada in a 54.5 kg catchweight bout at Shoot Boxing 2017 Young Cesar in Hanayashiki act.4 on October 14, 2017.
Kasahara scored a shoot point with a head and arm throw in the first-round, and badly staggered Yamada with a flurry of punches near the end of the last round.
[9] Kasahara faced Ryu, in his sixth and final fight of the year, at Shoot Boxing 2017 Young Cesar in Hanayashiki act.5 on December 17, 2017.
[14] Kasahara faced the second ranked Shootboxing super bantamweight Kyo Kawakami in the co-main event of Shoot Boxing 2018 act.4 on September 15, 2018.
[16] His 10–0 undefeated streak earned Kasahara the #2 ranking in the division, as well as the right to face Seiki Ueyama in the finals of the Shootboxing super bantamweight tournament, with the vacant title on the line.
[20] After successfully rebounded from his first professional loss, Kasahara moved up to featherweight to face Ponchan Bravegym at Shoot Boxing 2019 act.4 on September 28, 2019.
[23] He won the fight by a third-round technical knockout, stopping Lertchai with a flurry of punches in the final minute of the last round.
[26] The non-title bout was broadcast by Abema and was held in front of an empty arena, due to measures implemented to combat the COVID-19 pandemic.
[27] Kasahara lost the fight by a first-round stoppage, as he was knocked down three times by the midway point of the opening round, which resulted in a technical knockout victory for Nasukawa.
[39][40] On May 19, 2022, it was announced that Kasahara would face the reigning Krush Super Featherweight champion Chihiro Nakajima in a cross-promotional fight on June 19, 2022.
The bout was scheduled for the undercard of THE MATCH 2022, an Abema pay per view headlined by Takeru Segawa and Tenshin Nasukawa.
[42][43] Kasahara faced the second ranked RISE super featherweight contender Hyuma Hitachi at SHOOT BOXING 2022 act.4 on September 14, 2022.
[51] Kasahara faced the former Rajadamnern Stadium super bantamweight champion Singdam SunriseGym at SHOOT BOXING 2023 act.4 on September 23, 2023.