Tadasuke Makino scored his second Super Formula victory of the season after a charging drive at Motegi, but only after team-mate Kakunoshin Ota spun out of the lead.
Dandelion Racing looked firmly on course for a one-two finish heading into the closing stages of the 37-lap race, as Ota held a narrow lead over Makino.
Ota had run second behind poleman Kenta Yamashita (Kondo Racing) in the early stages, but managed to jump ahead by coming in when the pit window opened at the end of lap 10.
Makino meanwhile inherited second, having jumped from fifth on the grid to third on the opening lap, and circulated closely behind Yamashita until his stop on lap 22.
Kondo Racing driver Yamashita pitted the following lap, slipping behind Makino in the process, with Ota moving into the lead once all the mandatory stops were completed courtesy of his early stop and efficiency lapping slower cars.
Ota enjoyed an 11-second lead initially, but Makino started closing in at a rate of almost two seconds a lap, picking off another early-stopping car in the form of Toshiki Oyu in the process.
Makino caught up to the back of Ota with two laps to go, and the Dandelion pair proceeded to engage in a fierce battle for the win.
Ota looked like he might have done enough to hang on for victory when Makino ran wide attacking his team-mate at the Turn 10 hairpin.
But the following lap, Ota lit up his rear tyres and spun exiting the Turn 11 right-hander, stalling the engine and retiring on the spot – denying Dandelion a first 1-2 since 2012.
Although it initially appeared that Ota had made an error, the team suspects that a throttle issue caused his exit from the race.
Ota’s spin promoted Makino to his second win in the space of four races, 1.6s ahead of Yamashita.
Tomoki Nojiri completed the podium for Team Mugen, keeping himself five points clear of his new nearest rival in the championship Makino with four races left.
Kakunoshin Ohta, DOCOMO TEAM DANDELION RACING
Photo by: Masahide Kamio
Naoki Yamamoto was fourth for Nakajima Racing, while Sho Tsuboi recovered from eighth on the grid to finish fifth for TOM’S.
Nojiri, Yamamoto and Tsuboi all pitted relatively late, allowing them to make short work of Inging driver Oyu, who had pitted together with Ota on lap 10.
Oyu hung on for sixth position ahead of a recovering Ayumu Iwasa in the second of the Mugen cars, early stopper Kazuto Kotaka (Kondo), Nirei Fukuzumi in the best of the KCMG cars and Ren Sato in the second Nakajima machine.
Nyck de Vries completed his first Super Formula race in 13th for Team Impul, one place behind his Toyota World Endurance Championship stablemate Kamui Kobayashi (KCMG).
Sena Sakaguchi was the sole retirement of the race as his Inging machine ground to a halt on lap 17, but without causing a safety car.