The high-scoring Akita Northern Happinets met their match on Saturday night.
The Iwate Big Bulls held Akita to 4-for-28 shooting from 3-point range, which was a key factor in the hosts' 85-70 triumph over the previously unbeaten Happinets.
Akita (12-1) sits atop the Eastern Conference standings; Iwate (7-4) picked up a statement victory in the first meeting between the Tohoku rivals this season.