In the first wet Super GT race in three years, the superiority of the Michelin wet tyre told, giving both the #3 Nissan Z of Chiyo and Takaboshi and the #23 NISMO machine of Ronnie Quintarelli and Tsugio Matsuda a big advantage when conditions were at their worst.
But while the #23 led for a decent portion of the race after slicing into the lead from seventh on the grid, the #3 car gained the advantage by eliminating a pitstop.
Chiyo was among the first group of cars in the pits when the rain started to fall in earnest on lap 15 of 84, but then proceeded to stay out on wet tyres until the track had dried out enough to switch back to slicks on lap 55.
By contrast, Quintarelli braved it on slicks until the track had become completely soaked, pitting on lap 19, and then pitting again to hand over to Tsugio Matsuda on lap 44, the #23 taking a fresh set of Michelin wets.
On lap 54 Matsuda was in for slicks, but the extra stop left him more than 25 seconds down on the #3 Nissan, by now in the hands of Takaboshi.
Despite the arrival of more light rain in the closing stages, Takaboshi was able to nurse his advantage all the way to the flag, catapulting himself and Chiyo into the points lead with two races to go.
Behind the two Nissans, Mugen Honda duo Toshiki Oyu and Ukyo Sasahara completed the podium, with the speed of the Dunlop wet tyre allowing Oyu to establish himself in third before handing over to Sasahara on lap 36.
Pitting to his switch to slicks on lap 49, Sasahara managed to maintain his advantage over the chasing Cerumo Toyota GR Supra to score a first podium finish of the season.
The Cerumo machine of Yuji Tachikawa and Hiroaki Ishiura led the opening lap after Tachikawa barged his way by the pole-winning Bandoh Toyota for the lead at Turn 3, but once Tachikawa was on wet Bridgestones he was quickly swamped by the two Michelin-shod Nissans as well as the Dunlop-equipped Mugen Honda.
Ishiura repassed Sasahara for a net third but switching to slicks two laps later on lap 51 allowed the Mugen car back ahead, where it would remain.
From 14th on the grid, pre-race points leaders Bertrand Baguette and Kazuki Hiramine finished fifth at the wheel of the Impul Nissan despite carrying the stage three fuel flow restrictor.
Baguette had made his second stop on lap 27, one shy of the minimum cut-off, and then stayed out until lap 50 to hand over to Hiramine, who took slick tyres.
A short final stop and a well-timed switch to slicks allowed the pair to score six crucial points and stay within 3.5 points of new championship leaders Chiyo and Takaboshi.
The SARD Toyota of Yuhi Sekiguchi and Yuichi Nakayama finished sixth ahead of the Nakajima Honda of Takuya Izawa and Hiroki Otsu, who took their first points of the season in seventh.
Team Kunimitsu was the best of the Bridgestone Hondas in eighth, as Naoki Yamamoto passed the TOM’S Toyota of Giuliano Alesi in the closing stages.
Alesi and Sho Tsuboi were able to come from 15th and last to finish ninth by eliminating a pitstop, as Tsuboi stayed out on slick tyres in the early rain and waiting until the minimum cut-off lap to pit for wets and hand off to his teammate.
The #37 TOM’S Toyota of Sacha Fenestraz and Ritomo Miyata scored the final point in 10th.
GT300: New Toyota GR86 picks up first win
In the GT300 class, Inging pair Hiroki Katoh and Yuui Tsutsumi delivered the new-for-2022 Toyota GR86 a first victory.
Katoh and Tsutsumi got the advantage by making both the switch to wet tyres and then back to slicks at the perfect time, with Katoh among the majority of drivers to come in early on for a first pitstop when the rain started to fall.
A minority of cars opted to stay out, including the Team Studie BMW M4 GT3 of Augusto Farfus and the two Gainer Nissan GT-R NISMO GT3s, which all were able to make it as far as the pit window before making their first stops.
While several of the early-stopping cars made relatively early second stops to take more wet tyres and ended up having to stop again when the track dried, Katoh stayed out until it was dry enough to take slicks as he handed over to Yuui Tsutsumi on lap 49.
By staying out early on, both Gainer cars also managed to make it home on two pitstops, with the #11 car of Hironobu Yasuda and Keishi Ishikawa leading home the sister #10 machine of Ryuichiro Tomita and Riki Okusa.
The Studie BMW shared by Farfus and Ara looked good for a podium at one stage but lacked the pace of the Nissans when the track dried, and ended up slipping to fifth behind the Kondo Racing GT-R of Kiyoto Fujinami and Joao Paulo de Oliveira.
ARTA Honda pair Hideki Mutoh and Iori Kimura were also in the mix for a podium finish before Kimura picked up a drive-through penalty for making contact with the apr GR86.
That left Mutoh and Kimura in seventh at the finish ahead of the polesitting Subaru BRZ of Hideki Yamauchi and Takuto Iguchi, which ended up making three pitstops.
Fujinami and de Oliveira maintain a reduced four-point lead over Tomita and Okusa in the GT300 standings with two races left.
