Kubo returned to K-1 in 2017, and was immediately scheduled to take part in the 2017 K-1 Super Bantamweight Grand Prix.
[2] Kubo beat Suen Tak Chuen by an extra round unanimous decision in the quarterfinals, and Nobuchika Terado by a second-round knockout in the semifinals.
Kubo fought Yoshiki Takei in the finals, and lost the fight by unanimous decision.
[3] After he finished as the runner-up in the Super Bantamweight Grand Prix, Kubo was scheduled to fight a rematch with Nobuchika Terado for the Krush Super Bantamweight title, at Krush 82.
[5] Kubo was scheduled to fight a rematch with Yoshiki Takei for the K-1 Super Bantamweight title at K-1: K'FESTA.1.