Hirakawa was slowest of all in the Q2 pole shootout on Saturday, around eight tenths off the pace of poleman and title rival Tomoki Nojiri - with whom he had split the two wins at the opening Fuji Speedway double-header.
From 12th on the grid, the Impul driver was able to make up five places in a rain-soaked race on Sunday, as Nojiri finished second behind Nobuharu Matsushita.
It means Nojiri now has a 16-point advantage over Hirakawa in the title battle with seven races to go.
Drivers' standings after Suzuka:
| Pos | Driver | Points | Fuji* | Suzuka | AP | Sugo | Fuji | Motegi* | Suzuka* |
|---|---|---|---|---|---|---|---|---|---|
| 1 |  Tomoki Nojiri | 56 | 38 | 18 | - | - | - | - | - |
| 2 | Ryo Hirakawa | 40 | 36 | 4 | - | - | - | - | - |
| 3 | Nobuharu Matsushita | 20 | - | 20 | - | - | - | - | - |
| 4 |  Sacha Fenestraz | 20 | 11 | 9 | - | - | - | - | - |
| 5 | Ritomo Miyata | 19 | 19 | - | - | - | - | - | - |
| 6 | Tadasuke Makino | 16 | 5 | 11 | - | - | - | - | - |
* denotes double-header
Hirakawa admitted after qualifying that the car "didn't feel like it normally does" on Saturday, but was unable to put his finger on the cause.
"My qualifying lap was good, but the car wasn’t," Hirakawa told Motorsport.com. "From the start of practice I felt like I was missing grip at both front and rear, and when I put on new tyres it felt like I was on old tyres.
"The grip was not like it should be. Either the problem was something in the set-up or some difference in the tyres, we have to find out.
"But it's not like I was super-fast in qualifying at Fuji either, so it feels like our performance in qualifying is not good enough [in general]."
Post-race, he added: "There are seven races remaining, so I think we can catch up [to Nojiri]. But the main issue was the qualifying. The race was ok, so we are focused on [improving] qualifying."
Hirakawa started off Sunday by setting the fastest time in that morning's wet practice session, but said that the feeling of the car had changed yet again in the eight-minute warm-up immediately prior to the race.
The 2020 runner-up conceded positions off the line after a poor start, slipping to 14th on the opening lap, before steadily recovering ground, although he notably spent many laps stuck behind the Nakajima Racing machine of Toshiki Oyu before finally passing for seventh on lap 19 of 31.
"Unfortunately I didn’t feel as good as in the morning [practice]," said Hirakawa of his race. "In the warm-up I was not feeling the same. I was a bit shocked.
"And then I wore out the tyres trying to pass other cars. After passing Oyu I wasn’t fast enough to catch up, even in clear air. I was just doing 1m59s, 2m00s [laptimes], which wasn’t fast."
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