Izawa, who last raced in Super Formula in 2018 but remains active in SUPER GT, followed Ren Sato from Team Goh to work as an advisor for Nakajima ahead of last December's post-season test at Suzuka.
On the first day of official pre-season testing at the same track on Monday, it was revealed that Izawa will step up to the role of team director, as team founder Satoru Nakajima - who recently turned 70 - takes a step back to the more figurehead-type role of 'general manager'.
Izawa will therefore oversee the efforts of both Sato and three-time champion Naoki Yamamoto as Nakajima looks to turn around a recent dip in form in the first year with the new SF23 car.
"I think having Izawa as our team boss has led to considerably better performance," said Yamamoto, who set the second-fastest time on Monday behind reigning champion Tomoki Nojiri.
"I feel that the way we put together a plan, listening to the radios of both drivers, and applying what worked well for one driver to the other side... it has improved our efficiency a lot."
Semi-active drivers stepping up to team leadership roles has become a trend in the paddocks of both SUPER GT and Super Formula, as seen with Kazuki Hoshino taking over as team boss at Team Impul from his father Kazuyoshi.
However, Yamamoto is convinced that his former SUPER GT team-mate Izawa has qualities that make him particularly suited to leadership.
"It's not the case that any current driver would make a good team boss," said Yamamoto. "I know how intelligent Izawa is, and I never thought I would be able to work with him within the same team again like this, so it's very heartening."
Toyota outfit Rookie Racing also has a new leader this season in the form of two-time series champion Hiroaki Ishiura, who replaces Tatsuya Kataoka.
It was revealed on Monday that Kataoka will move across to TOM'S this year to work as an advisor for Giuliano Alesi.
