In an action-packed 450km race, a well-timed safety car period put Hiramine in a position to challenge for the win in the final stint, the Japanese driver having taken over from Baguette at the first round of pitstops.
After surviving a wild moment with the NISMO Nissan of Tsugio Matsuda in the battle for second, for which Matsuda was penalised, Hiramine was able to catch up with the Real Racing Honda NSX-GT of Koudai Tsukakoshi, who had taken the lead when a safety car mixed up the order.
With around five laps to go, Hiramine started closing in on Tsukakoshi at a rate of over a second a lap, and on lap 75 of 77 the Impul Nissan dived ahead at the hairpin to grab the lead.
Such was Tsukakoshi's loss of pace in the #17 car he shares with Nobuharu Matsushita that he lost 6.6 seconds in the remaining two laps until the chequered flag, only just holding off the SARD Toyota GR Supra shared by Yuichi Nakayama and Yuhi Sekiguchi.
The pole-sitting NISMO Nissan of Matsuda and Ronnie Quintarelli came home for fifth after its drivethrough penalty, gaining a place on the last lap when Naoki Yamamoto went off at 130R in the Team Kunimitsu Honda.
Impul's victory looked unlikely in the opening stint as Baguette was unable to make much progress from the back of the field, getting stuck behind the #37 TOM'S Toyota of Sacha Fenestraz for a number of laps before finally making the move.
Baguette was among the last of the GT500 drivers to stop, leaving it until lap 33 to hand over to Hiramine, who was suddenly vaulted up the order when the safety car came out on lap 49 following a crash for the Max Racing Toyota GR Supra GT300 car at 130R.
Along with the SARD Toyota of Nakayama, Hiramine was already in the pits when the safety car was deployed and the pits closed, while the leading four cars - led by the Mugen Honda of Toshiki Oyu - found themselves still having to make their second stops after the race resumed.
Tsukakoshi, who had taken over from Matsushita in the Real Honda on lap 29, assumed the net lead at this point, having been engaged in a three-way battle with the Mugen Honda and Cerumo Toyota of Hiroaki Ishiura at this stage.
This was thanks to what turned out to be an inspired decision to come in for a second stop on lap 48, which left Tsukakoshi leading Nakayama, Matsuda's Nissan, which had stopped on lap 41, and Hiramine.
When the race resumed on lap 55, Hiramine quickly passed Matsuda and then Nakayama, who subsequently dropped behind Matsuda on the next lap, but the Impul driver undid his hard work by running wide at 130R.
That put Matsuda back into second place, and it briefly appeared he might be in a position to threaten Tsukakoshi for the win, but it soon became clear that Hiramine was the man with the real pace.
On lap 65, Hiramine tried to pass Matsuda on the right-hand side exiting Degner 2 and approaching the hairpin, but Matsuda moved over in a late bid to block the move, sending Hiramine on to the grass and almost in the barriers.
Matsuda's subsequent penalty left Hiramine in second and with a 4.5s deficit to Tsukakoshi, but as the Honda driver faded dramatically, Hiramine closed in and made the winning pass to deliver his second GT500 win and a first together with new Nissan recruit Baguette.
The pair jump to the top of the championship standings with three races to go, 10.5 points clear of TOM'S pair Fenestraz and Ritomo Miyata - who finished eighth - and Real pair Tsukakoshi and Matsushita.
It also gives Nissan a fifth GT500 win in a row at Suzuka, continuing a streak that started in 2020.
