Stoffel Vandoorne took his first Formula E victory since his title-winning 2022 season thanks to a well-timed pitstop in the first Tokyo race.
Heavy rain washed out qualifying, with the grid set on morning practice times, and led to a delayed race start and initial safety car laps before the officials decided a standing start was safe.
Championship leader Oliver Rowland dominated the early stages from pole and looked comfortably on course for a fourth win of the season in his Nissan.
But then the race was red-flagged because Maximilian Guenther's DS Penske briefly showed 'red' status - denoting that it was electrically unsafe - as it came to a halt.
Maserati MSG driver Vandoorne, who'd started 14th, was the only driver who had managed to take a mandatory Pit Boost stop at that point, having deliberately heavily used energy early on to get into his pit window sooner.
He simply cycled to the front with a huge lead as everyone else pitted, having capacity to both lose several seconds with a half-spin and back off hugely in the final laps and still win by eight seconds.
Rowland fended off McLaren's Taylor Barnard and Envision driver Sebastien Buemi for second to extend his championship lead to 60 points, while Dan Ticktum scored a season-best fifth for Kiro ahead of Edoardo Mortara's Mahindra.
Andretti attempted to clear Jake Dennis's pitstop as the cars formed up on the grid for the restart but came in when the pit exit was closed so was black-flagged.
Leading finishers
1 Stoffel Vandoorne (Maserati MSG)
2 Oliver Rowland (Nissan)
3 Taylor Barnard (McLaren)
4 Sebastien Buemi (Envision)
5 Dan Ticktum (Kiro)
6 Edoardo Mortara (Mahindra)
7 Antonio Felix da Costa (Porsche)
8 Nyck de Vries (Mahindra)
9 Jean-Eric Vergne (DS Penske)
10 Robin Frijns (Envision)
