Heisei Ishingun
In December 1991, Koshinaka and Kuniaki Kobayashi were involved in a violent feud with karatekas Akitoshi Saito and Masashi Aoyagi. After their feud ended in the summer of 1992, the four eventually formed a stable that would eventually become Heisei Ishingun. Heisei Ishingun would also self-promote their own shows. They were also wrestle in WAR, which they feuded with several stars including Genichiro Tenryu, Ashura Hara, Takashi Ishikawa, Hiromichi Fuyuki, and Koki Kitahara, among others. In January 1995, Koshinaka teamed up with The Mad Dogs (Tatsutoshi Goto and Michiyoshi Ohara) to defeat Fuyuki, Jado, and Gedo to win the WAR World Six-Man Tag Team Championship, before losing the titles to Tenryu, Kitahara, and Animal Hamaguchi months later in June 1995. In July 1998, he won his second IWGP Tag Team title, this time with Tenryu, defeating Masahiro Chono and Hiroyoshi Tenzan. He and Tenryu would on to the titles until January 1999, when they lost the belts back to Tenzan and his new partner, Satoshi Kojima.