Japan fought back in tremendous fashion from one goal down to stun title contenders Pakistan 3-1 in the first upset of the Asian Champions Trophy hockey tournament here today. Japan were at the receiving end in the first session after Muhammad Rizwan had given Asian Games champions Pakistan the lead in the fifth minute. However, they hung on and equalised at the stroke of half time through Koji Kayukawa and then slammed two more goals through Kenta Tanaka in the last 10 minutes to ran away winners. It was the first defeat for Pakistan in three matches. They now have six points while Japan have four points from three matches. Pakistan's defeat left the tournament wide open as, apart from hosts China, all the teams have a chance of making it to the final.