Red Bull junior Lawson will begin Saturday's opening race of the 2023 season from the second row, after qualifying just two tenths slower than Mugen team-mate and reigning champion Tomoki Nojiri.
That's despite the New Zealander having no prior experience of Fuji, a situation exacerbated by Friday's free practice session being cancelled due to poor weather.
Speaking after qualifying third, Lawson said he never expected to be so high up the grid for his first start in Japan's premier single-seater series.
"I’m happy, but more relieved than anything because before the session I had absolutely no idea how it was going to go," he admitted.
"I did the first run on used tyres just to learn the track, treated it like a practice session, and then from mid-session we put on new tyres and went into qualifying mode.
"Very happy to come away with third, I wouldn’t have believed you if you had said that at the start of the session. It shows how the team has done a fantastic job to have a baseline as good as this straight away, having never tested this car at this track.
"Obviously the car is not perfect, and I am nowhere near being perfect either, but it shows what a good job they did."
Lawson will make his Super Formula race debut later on Saturday at Fuji, and faces the challenge of mastering the series' tricky hand-clutch.
Tyre degradation is also expected to be a factor in the 41-lap race with new-spec Yokohama tyres made partly from sustainable materials.
"I’ve never done a start in this car before, so that will be stressful, but once we get off the line I can start to settle into a groove," said Lawson.
"I have no idea [about tyre degradation], I can only judge from Suzuka [pre-season testing], and we had a bit of tyre deg there. Potentially there could be quite high deg in sector three, but I don’t know exactly how it’s going to be. Everybody’s going to be taking a shot in the dark."
In last month's pre-season test at Suzuka, Lawson moved to play down expectations of challenging for wins early in the campaign.
After coming so close to Nojiri's pace in qualifying, the 21-year-old remains hesitant to say that he expects to be fighting at the front of the field regularly.
"There is a lot to learn still and improve on," he said. "Once we get the first weekend done, I’ll have a better idea of where we are.
"One qualifying isn’t enough to be satisfied to say for sure I’ll be racing at the front [all season]."
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