[1] Koki made his professional debut against Shun in September 2015, winning the fight by knockout.
[2] He suffered his first loss at Krush 72, losing to Akihiro Kaneko by a third-round knockout.
[3] He rebounded with a first round TKO of Reiji Kasami at Khaos 2,[4] This victory was followed by losses to Aoshi and Junya Weerasakreck, as well as a draw with Naoya Otada.
[5] After this bad run of form, Koki won his next three fights against Yuta Kuwata, Taisuke Degai and Shuto Hagiwara, all by decision.
[10] Koki was scheduled to fight a rematch with Akihiro Kaneko at K-1 World GP 2021: Yokohamatsuri on September 20, 2021.