Nagashima was part of last year's winning Honda squad alongside Lecuona and Takumi Takahashi, but was replaced by Xavi Vierge when the marque made its initial 2023 announcement last month.
That was in part due to a foot injury that Nagashima had sustained earlier in the year, but he returned to action in official testing earlier this month and set the fastest time across the two days.
Now, Honda has announced Nagashima will step back up to the race team after all, with Lecuona now unable to race at Suzuka due to being chosen to step in for an injured Alex Rins for the clashing MotoGP race at Silverstone.
“I am truly honoured to be able to participate in the Suzuka 8 Hours again this year," said Nagashima. "I would like to thank Honda and HRC for giving me this opportunity.
"I’m feeling good about my preparations as the tests went well, but I will keep up my concentration leading up to the race in August.
"I am looking forward to contributing to Team HRC’s consecutive victories, and I hope all of our fans will support us.”
Honda has also announced that Team HRC, which keeps the #33 for its title defence, will carry title sponsorship from Japan Post.
Nagashima's best time in testing, a 2m06.077s, put the works Honda squad almost six tenths clear of the opposition, with the brand's fleet of CBR1000RR-Rs monopolising the top three in the combined standings.
Astemo Honda Dream SI Racing (Kosuke Sakumoto/Ryo Mizuno/Kazuma Watanabe) concluded the test second-fastest ahead of the FCC TSR Honda France (Josh Hook/Mike di Meglio/Alan Techer).
Yamaha's semi-works YART squad (Niccolo Canepa/Marvin Fritz/Karel Hanika) was fourth-fastest.
The Suzuka 8 Hours is set to take place on 4-6 August.
