[5] Kai and his brother, Mikuru Asakura, spent much of their childhood getting involved in numerous street fights.

The brothers would often fight each other as well, to which Kai attributes his toughness as a professional mixed martial artist.

As they were entering their adolescent years, at the suggestion of a therapist, their mother enrolled them into boxing classes.

[8] Asakura began his professional career under the banner of DEEP, when he faced a fellow debutante Tomoya Suzuki.

[10] Two months later he faced Keigo Takayama winning the fight after just 40 seconds via technical knockout.

Asakura won the fight after 29 seconds, hitting Heili with a short left hook, followed by a knee strike.

[16] Asakura suffered his first career loss to Je Hoon Moon during Road FC 39, losing via technical knockout.

[18] Kai won the fight in the second round after knocking Saiga out with a grounded knee.

After suffering an early knockdown, he went on to win a split decision, which would be named as a Fight of the Month nominee for May of 2018 by MMA Junkie.

Asakura faced Manel Kape in a rematch for the vacant Rizin Bantamweight Championship.

Kape knocked Kai down twice in the beginning of the second round which forced the referee to stop the fight.

[32] Asakura faced former Lightweight King of Pancrase Shoji Maruyama at Rizin 24 – Saitama.

[36] Asakura faced Shooto Watanabe in the opening round of the Bantamweight Grand Prix at Rizin 28 on June 13, 2021.

[41] He won the fight by unanimous decision, and advanced to the tournament finals, where he faced Hiromasa Ougikubo.

[48] However on July 18 it was announced that Asakura withdrew due to injury and was replaced by Hiromasa Ougikubo.