Diamond Ring was an independent Japanese professional wrestling promotion that, until 2012, was known as Kensuke Office. The promotion was founded by and is owned by puroresu legend Kensuke Sasaki, who has owned and operated it since its creation in 2005. In February 2014 the promotion ran its last card, after which Sasaki announced his retirement.
They featured storylines with the Diamond Ring stable with the Voodoo Murders. On 5 October 2013 Nakajima received an opportunity for the GHC Heavyweight Championship and he lost to the defending champion Kenta. On September 9 Kento Miyahara announced that he was officially breaking off his affiliation with Diamond Ring and becoming a freelancer. On 24 November 2013 the Voodoo Murders did their last match on Diamond Ring and left the promotion and jumped to Pro Wrestling Zero1. On February 11, 2014, Sasaki suffered his first loss to Katsuhiko Nakajima in the main event of a Diamond Ring event, later that day Satoshi Kajiwara made his last match on the promotion and retired.Two days later, Sasaki held a press conference to announce his retirement from professional wrestling. Following Sasaki's retirement, Diamond Ring was left with only one remaining wrestler, Katsuhiko Nakajima, with Satoshi Kajiwara resigning and Mitsuhiro Kitamiya joining Pro Wrestling Noah. On March 09 they held their last show named Diamond Ring Hometown Match and after that night they closed the promotion but the stable it was represented by Nakajima until 2015 when Nakajima joined to Pro Wrestling Noah he started to no longer represent the group.