Tsuboi and Miyata carved their way through from 12th on the grid to score their second win of 2023 aboard the #36 Toyota GR Supra and take a seven-point lead in the championship with only the season finale left to run.
In a thrilling and unpredictable 450km race, Miyata caught the long-time leading ARTA Honda of Hiroki Otsu in the closing stint of the race, with the pair engaging in a fierce duel for the top spot.
Otsu had taken over from team-mate Nirei Fukuzumi in the #16 ARTA NSX-GT on lap 59 of 97, while Miyata - who replaced Tsuboi at the wheel of the #36 car at the first round of pitstops - made his final stop on lap 65.
But Miyata fought through from a net fifth place to grab second within a matter of laps, dispatching the points-leading NDDP Racing Nissan of Mitsunori Takaboshi in the process, before closing down Otsu's five-second lead.
By lap 80, Miyata had caught up to the back of Otsu, and after several laps of on-the-limit dicing through the traffic, Miyata made the decisive move up the inside at the Turn 11 hairpin on lap 87.
Miyata went on to take the chequered flag by five seconds, as Otsu held off the NDDP Nissan that Takaboshi took over for the final stint from Katsumasa Chiyo.
The result means that the top three cars in the race are the only cars that can still win the championship in the season finale at Motegi: Fukuzumi and Otsu will head to the finale as rank outsiders in third, 13 points behind Tsuboi and Miyata with 21 on offer.
Source: Autosport