The number of participants in the New Japan Cup has varied over the years, from a lowest of 14 in 2007 and 2009 to a highest of 48 in 2022; the 2021 tournament features 30 entrants.

[8] Giant Bernard and Hiroyoshi Tenzan received byes to the second round, due to their victories in the 2006 New Japan Cup and G1 Climax respectively.

Shinsuke Nakamura was injured in a non-tournament match on March 13, giving Tenzan an additional pass to the semifinals.

The winner, Yuji Nagata, went on to defeat Hiroshi Tanahashi for the championship on April 13, beginning his second reign with the title.

The eventual winner of the tournament, Hirooki Goto, went on to lose the IWGP Heavyweight Championship match to Hiroshi Tanahashi on May 3 at Wrestling Dontaku 2009.

Goto went on to challenge the IWGP Heavyweight Champion Shinsuke Nakamura on April 4, but would once again fail in his attempt to win the title.

[27] The winner of the tournament, Kazuchika Okada, went on to defeat Hiroshi Tanahashi for the IWGP Heavyweight Championship at Invasion Attack on April 7.

[47] Tomoaki Honma was originally announced for the tournament, but was pulled out and replaced with Yuji Nagata after suffering a spinal cord injury.

[63] The original card for the New Japan Cup, when it was scheduled to take place from March 4 to March 21, had to be completely re-worked for the eventual final card, as several wrestlers who originally planned to participate could not go to Japan when NJPW resumed its activities due to travel restrictions amid the pandemic.

Of the 32 wrestlers included in the original card, 14 were not a part of the eventual tournament in June–July: Alex Coughlin, Bad Luck Fale, Chase Owens, Colt Cabana, David Finlay, Karl Fredericks, Jay White, Kenta, Jeff Cobb, Juice Robinson, Mikey Nicholls, Tanga Loa, Toa Henare, and Will Ospreay.

[65] Evil and Hiroshi Tanahashi received byes on account of being the previous edition's winner and the reigning NEVER Openweight Champion respectively.

At the semifinals on March 20, the match between Kazuchika Okada, Hiroshi Tanahashi and Kota Ibushi and Bullet Club's Jay White, Kenta and Yujiro Takahashi was stopped due to a 7.0 magnitude earthquake that occurred in the Miyagi prefecture.

While Bullet Club went backstage; Okada, Tanahashi, and Ibushi stayed in the ring area to calm the crowd and pose for pictures while New Japan employees were performing safety checks throughout the arena, which took about half an hour.

After the safety checks were made, the match was able to continue with ring announcer Makoto Abe informing attendees shortly beforehand the rest of the event would be canceled if they were any additional aftershocks.