Nagashima, 30, joined Honda last year after a four-year spell as a full-time Moto2 rider came to an end following the 2020 season, in which he finished eighth overall after winning the Qatar season opener.
Besides a handful of outings in the middleweight class for Italtrans as a replacement for an injured Lorenzo Dalla Porta, Nagashima mostly spent 2021 on the sidelines, spending his time preparing for Honda's ultimately successful attack on the Suzuka 8 Hours this year.
