[10][11] Tsubakihara was inspired to pursue martial arts at the age of five, after seeing an episode of the Fist of the North Star anime, which motivated him to begin training Shōrin-ryū karate at the Gesshinkai Team Samurai.

He would win the Kyoken Middleweight title with decision victories over Taiga Imanaga and Taiki Kiyama in the semifinals and finals respectively.

[15] Following his third title defense, Tsubakihara took part in the 2015 K-1 Challenge A-Class tournament, competing in the 60 kg weight class.

He fought the second round of the tournament, against Kaito Nagashima, on July 30, 2016, two months after making his professional debut at the age of 17.

He won the first three bouts of the tournament against Nagashima, Souta Saito and Yuta Hayashi, but once again fell short in the finals, losing a unanimous decision to Taito Gunji.

He managed to win the tournament in his third attempt, beating Toki Tamaru in the semifinals and Itsuki Kobori in the finals.

He notched his first professional victory against Tatsuya Izumi at ALL BOX WORLD 9th, winning the fight by a second-round knockout.

The other tournament pairings pitted Taito Gunji against Riku Morisaka, Shota Oiwa against Masashi Kumura and Shoya Masumoto against Victor Saravia.

[28] The fight was as close as their previous three bouts, with Gunji winning a split decision, after an extra round was fought.

During the post-fight press conference, Tsubakihara asked for a fight at the K-1 World GP 2020 in Osaka, his hometown.

[35] Tsubakihara was granted his request, as he was scheduled to fight the newly crowned K-1 Featherweight champion and the 2019 K-1 "Fighter of the Year" Yuki Egawa.

[38] Tsubakihara kept to his patented outfighting style, keeping distance from Egawa and scoring points through jabs and front kicks.

[39][40] During the post-fight conference, Egawa revealed he had suffered a fracture of the index finger on his left foot, three weeks before the bout, and called for a rematch with Tsubakihara.

[3] Tsubakihara came under criticism for his outfighting style, perceived as boring by the fans, who called for a change in the K-1 ruleset to make for more exciting fights.

[47] Tsubakihara was scheduled to fight Shuhei Kumura in a non-title bout at K-1 World GP 2021: Japan Bantamweight Tournament.

Tsubakihara and Gunji fought four times previously, with each holding a single win and loss against the other as amateurs and professionals.

[57] Tsubakihara faced the reigning Krush Featherweight (-57.5kg) champion Riku Morisaka at K-1 World GP 2023 in Yokohama on June 3, 2023.

The bout was a rematch five years in the making, as Tsubakihara had previously overcome Morisaka by unanimous decision at KHAOS 5.