Kai started training martial arts at the age of six under his father Kai Kamaka Jr., who owns the 808 Fight Factory in Hawaii.[4] Kai has a brother named Tristin Kamaka who is a former University of Hawaii Football receiver. Kai attended Pearl City High School where he wrestled and eventually won the HHSAA State Championship after claiming gold in OIA conference finals.[5][6] For his wrestling accolades, he received a wrestling scholarship to study at Midland University from where he graduated with a bachelor's degree.[4][7]
Mixed martial arts career
Early career
In his MMA debut at KOTC Mana, he faced Anthony Reyes and went on to defeat him via unanimous decision. Kamaka submitted Nui Wheeler at Destiny Na Koa 6 via rear-naked choke in the first round. After losing his next two bouts against Andrew Natividad and Jeff Mesa, at KOTC Energetic Pursuit, he defeated Rick James via unanimous decision. Kamaka iii defeated Mauricio Diaz via unanimous decision at KOTC Highlight Reel.[8]
Bellator MMA / LFA
Kamaka faced Shojin Miki at Bellator 213 on December 15, 2018. He won the bout via unanimous decision.[9]
Kamaka faced Spencer Higa at Bellator 236 on December 21, 2019. He won the bout via unanimous decision.[10]
After winning a unanimous decision against Michael Stack at LFA 87 on July 31, 2020, he got the call to make his UFC debut on extremely short notice.[11]
Ultimate Fighting Championship
Kamaka made his UFC debut against Tony Kelley at UFC 252 on August 15, 2020. He won the bout via unanimous decision.[12] This bout earned him a Fight of the Night bonus award [13]
Kamaka faced Danny Chavez, replacing injured Choi Doo-ho, on July 31, 2021 at UFC on ESPN 28.[18] Kamaka was deducted a point in round two for an illegal groin strike, as a result the fight was ruled a majority draw.[19] 11 out of 13 media outlets scored the bout as a win for Kamaka.[20] The bout was the last of his contract and Kamaka decided to test free agency, parting with the UFC.[21]
Return to Bellator MMA
On September 28, 2021, Kamaka signed a contract with Bellator to return to the promotion for the second time.[22]
Kamaka, replacing Keoni Diggs, faced John de Jesus on December 3, 2021 at Bellator 272.[23] He won the bout via unanimous decision.[24]
Kamaka faced Justin Gonzales on April 23, 2022 at Bellator 279.[25] He lost the close bout via split decision.[26]
Kamaka was scheduled to face Akhmed Magomedov on July 22, 2022 at Bellator 283.[27] Kamaka however pulled out of the bout due to unknown reasons.[28]
Kamaka faced Kevin Boehm on December 9, 2022 at Bellator 289.[29] He won the fight via TKO in the third round.[30]
Kamaka faced Adli Edwards on April 22, 2023 at Bellator 295.[31] He won the bout via unanimous decision.[32]
Kamaka was rebooked against Akhmed Magomedov on August 11, 2023 at Bellator 298.[33] However, Magomedov pulled out of the bout a week before the event.
Kamaka faced Henry Corrales on October 7, 2023 at Bellator 300.[34] He won the fight via split decision.[35] 4 out of 4 media scores gave it to Corrales.[36]