Ticktum started sixth and went early with both PIT BOOST and ATTACK MODE to emerge from the stops as the net leader.
Dennis, though, had the overlap on the rest with his 50kW, all-wheel drive boost and by the end of Lap 29, he made it by Cassidy then Ticktum to hit the front.
RESULTS: The 2026 TDK Tokyo E-Prix Round 14
From there, it looked to be comfortable, with Ticktum also seeming to settle for a strong second with a message over Team Radio.
However, right at the last - through the penultimate turn, ahead of the final chicane, Ticktum spied his chance to jump Dennis as the Andretti driver lifted early with energy critical. He made the move stick and led his compatriot home to make it nine different winners in the last nine rounds, with the closest winning margin of the season - his second in Formula E.
The pair led home Cassidy; the New Zealander securing a podium on a poignant weekend for Citroën Racing following the tragic news of Team Principal Cyril Blais' passing.
Standings leader Pascal Wehrlein (Porsche) tangled with rival Antonio Felix da Costa (Jaguar TCS Racing) and failed to finish, which fired Dennis right back into the Drivers' mix. Jaguar's Mitch Evans also profited, rounding fourth to hit top spot in the Drivers' table - 144 points to Wehrlein's 141. Edo Mortara took advantage, too, with a strong fifth.
Jaguar TCS Racing extended its Teams' advantage over Porsche, with Porsche returning the favour in the Manufacturers'.
Formula E returns for the 2026 TDK Tokyo E-Prix Round 15 at the same time on Sunday 26 July.
As it happened...
Dennis led the pack away as the 20 cars funnelled through the tight first sector - sadly not unscathed as Nico Mueller and Nyck de Vries both needed to pit for repairs after contact through that opening lap; the former squeezed by da Costa.
Lap 10 and Dennis led Mortara, da Costa - who made it back by Barnard at Turn 1 with the Brit now fourth - Ticktum, Cassidy, Wehrlein, Guenther, Vergne and Nato.
Buemi was first to jump for his 50kW, all-wheel drive ATTACK MODE boost, and clambered to second - up 12 spots on his grid slot come Lap 17, finally muscling by Edoardo Mortara.
Drivers started to hit the PIT BOOST window, with Guenther, Nato, Eriksson, Ticktum and Cassidy the first to jump. In the melee, da Costa was fed into the wall but managed to carry on. Wehrlein was the driver he clashed with, and the standings leader was left worse off and with front wing damage - passed by Evans and left 12th and eventually forced to retire.
Dennis remained out front and jumped into the pits some time later on Lap 21. He emerged behind compatriot Ticktum who'd gone for ATTACK MODE to make up enough ground to hit the front.
Ticktum was the eventual race leader once it all shook out, with Mortara, Cassidy and Dennis four, six and seven seconds back - but the latter pair both in ATTACK and making up ground fast.
Mortara again put up a staunch defence with Cassidy finally able to squeeze by ahead of Turn 16 on Lap 28 for P2. Dennis still had a couple of minutes' ATTACK to use with the Brit third, by Mortara and chasing Cassidy - the pair both a couple of second back from leader Ticktum.
Dennis dispatched Cassidy in quick time, and within another lap, on Lap 29, Dennis had caught the leader with 20 seconds of ATTACK to play with. Dennis made it by on the lead up to the final chicane for the race lead.
Evans and Rowland went late with their ATTACK MODE activations, with energy in-hand. The Kiwi managed to climb up to fifth once his 50kW boost came to an end.
From there, Dennis looked like he'd control things to the flag but right at the last, into the final couple of corners Ticktum jumped Dennis for the win - the pair heading home Nick Cassidy who sealed an emotional podium for Citroen Racing.
SCHEDULE: Where, when and how to watch or stream the 2026 TDK Tokyo E-Prix, Round 15
Free Practice 3: Sunday 26 July, 13:30 local / 05:30 BST
Qualifying: Sunday 26 July, 15:40 local / 07:40 BST
Race: Sunday 26 July, 20:05 local / 12:05 BST
View the full schedule in your time zone and check the broadcaster listings or tap the Ways to Watch button above to find out where to watch all the racing action where you live.
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