Heisei Ishingun
After Heisei Ishingun disbanded, Koshinaka rebounded and regained the IWGP Tag Team titles in March 1999, this time with Kensuke Sasaki. He and Sasaki held on to the belts until June 1999, when they lost the belts to The Mad Dogs. In the summer of 2000, AJPW and NJPW were working together after the Pro Wrestling Noah exodus nearly killed AJPW. This led Koshinaka to return to his home promotion after fifteen years. He took part in a tournament for the Triple Crown Heavyweight Championship that was vacated by Kenta Kobashi; he defeated Johnny Smith in the first round, but lost to Toshiaki Kawada in the semi-finals. In January 2003, Koshinaka's contract was not renewed by NJPW officials.