 Afterwards, he had a short stint in Fighting Network Rings, losing to Chris Haseman by doctor stoppage from a cut at the event Extension Fighting 2.He retaliated by defeating Haseman in another Rings event, Battle Genesis Vol.2.In 1998, Otsuka debuted in worldwide MMA for PRIDE Fighting Championships in PRIDE 4, the same event in which fellow pro wrestler Nobuhiko Takada had his rematch against Rickson Gracie.