Just two weeks after his first non-scoring race of the season in Portugal, Championship leader Andrea Dovizioso came back at the front of the 125cc scene with victory in the crash-strewn Japanese GP. At the start of the Camel Grand Prix of Japan, Héctor Barberá beat Casey Stoner, Dovizioso and Roberto Locatelli to the holeshot, but the Australian was prompt to seize the lead from the young Spaniard. On the second lap, a gearbox lever failure put an end to Stoner's promising opening and allowed Dovizioso to take first.

A thirteen-lap restart would eventually determine the ultimate classification. For the new start, the front row featured Dovizioso, Locatelli and Corsi according to the race standings before the interruption of the race, while Barberá and Lorenzo had to restart from the back of the grid. Both Spaniards weren't able to join the grid in time for the warm-up lap due to mechanical issues.

Despite a strong start, Locatelli saw Dovizioso remaining right on his tail. Both riders swapped the lead a few times. In a decisive last lap, Dovizioso was back in first position when Locatelli crashed before being able to make his move. The former World Champion was able to rejoin the race to take the flag in 14th.

"It was a tough race," commented Dovizioso, who extended his Championship lead to 45 points over Barberá and 52 points over Locatelli. "I was very quick in the first part of the race, but it wasn't the case after the second start. I had to stay behind Locatelli but I tried and passed him, I wanted to go for the win. He crashed on the last lap, it's a shame for him, but I'm really happy with the result." – 19 September 2004