Fumio Nishimura and Tyler Stone sparked the Chiba Jets in the decisive fourth quarter on Saturday with a combined 18 points (nine apiece), and the visitors finished strong to earn an 84-77 victory over the Tochigi Brex.
A Brex victory would have clinched the East Division title.
Instead, Tochigi (44-12) goes back to the drawing board for Sunday's rematch, the series finale at Brex Arena Utsnomiya. The Jets' magic number remains one.