Oshima came home fourth in the solo Rookie Racing entry on Sunday, marking his best result in a single-seater since his third-place finish at Autopolis in 2019.
Since joining the Rookie squad owned by Toyota chairman Akio Toyoda in 2020, Oshima has often featured towards the rear of the field, with just a handful of points of finishes to his credit in that time - and concluded the 2022 campaign with zero points.
However, the 36-year-old was seemingly rejuvenated by the switch to the new SF23 chassis, as well as changes to the Rookie team structure, including the recruitment of two-time champion Hiroaki Ishiura as team director.
Reflecting on a result that prompted celebrations in the Rookie camp after the chequered flag, Oshima said: “For the last few years I’ve been pretty much last, so even I was starting to doubt myself, thinking, ‘Maybe you’re just slow in a formula car…’
“But even so, Akio-san always told me, ‘You’re fast, so don’t worry about it!’ I’m really glad I could finally live up to his expectations.
“I’m sure Akio-san is very busy, but he tells me, ‘I’ve come here to enjoy myself in my free time.’ He was so happy he was welling up, and I was close to tears as well… I know I shouldn’t cry about fourth place though, so I was just about able to hold myself together!
“I’ll do my best so that the next time we finish fourth, it will be frustrating.”
Key to Oshima’s result was his grid slot of eighth, by far his best of the year so far, and a commitment to pitting as soon as the window opened on lap 10 of 51.
That allowed the veteran to jump ahead of many of the cars that had started in front of him, including Red Bull junior Liam Lawson, whom he held at bay for fourth in a final-lap battle.
After qualifying, Oshima told Motorsport.com he was hopeful that the improvements the Rookie team had found at Sugo would translate to improved results at other tracks.
“Even from Autopolis, the car felt not too bad in practice, we just made a mistake on the set-up for qualifying,” he explained. “This time we changed a lot, we made a big step on the suspension set-up, which worked well in these conditions.
“I was still struggling for rear grip, the balance was not good, but the grip level was high, so that’s why I could qualify well.
"I think this set-up can work at every track, and also the way the car is assembled and the organisation of the mechanics is improving.”
Kobayashi unmoved by season-best P6
Immediately behind Oshima in the closing stages at Sugo was the KCMG machine of Kamui Kobayashi, who finally conceded a place to Lawson on the final lap to come home sixth - also his best result of the season so far.
But Kobayashi was keen to downplay the significance of the result for the team, even as Yuji Kunimoto made it two KCMG cars in the points in ninth.
“This weekend we did a good job with the set-up, especially as qualifying was a disaster because of the yellow flag [for Cem Bolukbasi’s crash]," Kobayashi told Motorsport.com. "The race was quite smooth.
“But every race is different, and this track is a bit special. Still we need more time, we need to understand things more, and we’ll see.”
