The 2021 series runner-up endured a trying first season with the one-car Drago squad following his off-season move from Dandelion Racing, scoring points just once all year with eighth place at Sugo.
In a bid to bring more set-up ideas to the table, Drago opted to run ex-Team Goh driver Atsushi Miyake for the opening day of the Suzuka test, before Fukuzumi took over the #12 car for the second day.
Fukuzumi, who was 11th-fastest that day, has since been confirmed to be driving for Drago for a second season in 2023.
But the 25-year-old feels that the team didn't manage to get any closer to solving the long-run pace issues that held it back this year.
"The main thing we did in the test was trying to find the causes of our weaknesses," Fukuzumi told Motorsport.com's Japanese edition. "But to be honest, I don’t think we learned that much.
"There were a lot of parts we struggled with and things that weren’t good. We couldn’t find anything that worked really well or really badly [despite trying a lot of different set-ups]. We have to keep working to find the cause.
"The important thing is to make a stronger car for long runs. That was our main issue this season, so I want to keep that in mind for the next test."
Even the introduction of an updated car with a revised aerodynamic package has not left Fukuzumi feeling confident of a Drago revival, as he feels that such a change could end up favouring the series' larger outfits.
"I’m sure the strong teams will be at the front," said Fukuzumi. "The team that anticipates this best and analyses the data best will fare best.
"I also feel like the differences between the strongest teams and the weaker teams will be clear. If we don’t analyse what we learned in the test and prepare well for next year, the results will be similar, so we have to work hard."
Fukuzumi also confirmed that the key personnel for the 2023 season at Drago are set to remain unchanged, with Ryou Arai remaining the chief engineer.
"It will be tough if we don’t have some kind of extra impetus," he added. "But we have to do the best with the structure we have now."
