Japan's director of rugby Masahiro Kunda and interim coach Mark Hammett named a 43-man squad on Tuesday ahead of their Tests with Canada and Scotland in June.
Nineteen members of the Brave Blossoms squad at last year’s Rugby World Cup have been included.
There are also 19 members of the Sunwolves in the squad, which will be cut to 30 following the weekend of May 28-29 when Japan play Hong Kong in the Asia Rugby Championship and the Sunwolves take on the Brumbies.
"I am very excited to see the naming of the new Japanese rugby team," new head coach Jamie Joseph said from New Zealand.
"After a successful RWC2015 campaign it is important we now look to the future and the squad that has been named today should excite all rugby fans in Japan.
"I can’t wait to join the team in September in preparation for November tour and would like to congratulate all the players for their selection today.
"Canada and Scotland will be a huge challenge for the Brave Blossoms in their first hit out of the international season but I am sure the team will do us all proud.”
With Joseph unavailable to lead the side until later in the year, Hammett will take over from Ryuji Nakatake, who is coaching the Brave Blossoms during the ongoing Asia Rugby Championship.
"This is a really important time for the Japan national team,”" said Hammett.
"This is the start of a new build-up towards Rugby World Cup 2019. All nations go through a rebuilding phase after a World Cup and the achievements of the 2015 side didn’t just happen last year.
"They happened over a long period of time."
Michael Leitch has been included in the squad, as have all Japan’s overseas based players with the exception of Hiroshi Yamashita, who has opted to remain in New Zealand in June to train with the Chiefs.
Four students have been included in the squad and seven of the 43 are uncapped.
"This is a really good opportunity to see players that can perform at test level,” added Hammett, who is joined in the squad by 19 of his Sunwolves squad.
"We can assess new leaders and it gives the players a chance to develop more test experience."
The Brave Blossoms play Canada in Vancouver on June 11 and then take on Scotland in Toyota City on June 18 and in Tokyo on June 25.
Forwards: Takuma Asahara, Taiyo Ando, Shoji Ito, Keita Inagaki, Kazuhiko Usami, Hitoshi Ono, Shinnosuke Kakinaga, Takeshi Kizu, Shokei Kin, Jiwon Koo, Naohiro Kotaki, Hendrik Tui, Kensuke Hatakeyama, Yoshiya Hosoda, Ryu Koliniasi Holani, Kyosuke Horie, Shota Horie, Amanaki Lelei Mafi, Masataka Mikami, Futoshi Mori, Kotaro Yatabe, Hiroki Yamamoto, Michael Leitch
Backs: Keisuke Uchida, Kosei Ono, Kentaro Kodama, Ayumu Goromaru, Male Sau, Hosea Saumaki, Yasutaka Sasakura, Kaito Shigeno, Harumichi Tatekawa, Fumiaki Tanaka, Yu Tamura, Ryoto Nakamura, Ryuji Noguchi, Mifi Poseti Paea, Karne Hesketh, Tim Bennetts, Kotaro Matsushima, Rikiya Matsuda, Hajime Yamashita, Ryohei Yamanaka