On lap 18 of the 52-lap race, Makino and Cassidy were running in eighth and ninth places respectively, and were among the first cars to make their mandatory pitstops.
But when Makino brought in the #100 Kunimitsu Honda he shares with Naoki Yamamoto into his pit stall, there was significant left-rear damage, and while Yamamoto was ready to take over at the helm, the car was wheeled into the garage to be repaired.
Moments later, the TOM'S Toyota that Cassidy was handing over to Hirakawa was seen carrying damage to the nose, suggesting the two cars had come together on-track.
#37 KeePer TOM'S GR Supra
The #37 car was awarded a drive-through penalty for the incident, which was served by Hirakawa shortly after a mid-race safety car period, and several laps later Hirakawa pitted to retire the damaged GR Supra.
Makino said that the fact Cassidy was penalised showed clearly the Kiwi was to blame.
"Nothing happened, except Nick just hit me," Makino told Motorsport.com. "He got a penalty. I think that says everything."
Asked he felt he had braked early, Makino said: "No, just normal [speed] before the 50 [km/h] line. I was under 50, which is pretty normal."
Yamamoto did eventually take to the track with a fresh, unpainted rear bumper after the repairs, finishing 20 laps down in 14th - and a lap ahead of the TOM'S car.
The incident ends a 12-race points-scoring run for Cassidy and Hirakawa, although they remain only a single point away from the lead of the championship following Kazuya Oshima and Sho Tsuboi's failure to score, with three more crews just a further point back.
"It was completely perfect stint," reflected Cassidy. "I was around 8km/h slower than #36 [the sister TOM'S car] and could keep them behind and have stronger pace at the end.
"I didn’t expect to pass #14 [Oshima in the Cerumo Toyota] around outside in first sector, and I could do a good move on #17 [Bertrand Baguette's Real Racing Honda]. It was just a shame to finish like that after no mistakes and great pace."
#37 Team TOM'S Toyota GR Supra: Ryo Hirakawa, Nick Cassidy