Nakajima continued to wrestle for WJ for a short time, even wrestling the original Tiger Mask Satoru Sayama before signing with Kensuke Office in April. This led to his debut with New Japan Pro-Wrestling, facing legendary junior heavyweight Jushin Thunder Liger in the Tokyo Dome on May 3, 2004. He made his debut with All Japan Pro Wrestling the next day, successfully teaming with Toshiaki Kawada in a six-man tag team match. He continued to wrestle for both promotions extensively throughout 2004, even competing in Block B of NJPW's Best of the Super Juniors tournament, finishing with two points by defeating Curry Man and reaching the finals of the Young Lion "Toukon" ("fighting spirit") tournament, losing to Ryusuke Taguchi.