Baba Diawara headed home the equaliser two minutes in to stoppage time to make it 3-3 and keep the Reds in second place in Group H with five points.
Adelaide will be waiting anxiously for the result of the clash between Korean side Jeju United and group winners Jiangsu Suning, which kicked off as United's match ended.
The Reds endured a horror start in Japan when towering striker Shun Nagasawa outjumped goalkeeper Eugene Galekovic to meet Yasuhito Endo's near post corner and power a header into the net on six minutes.
Gamba doubled the advantage six minutes later after a stunning goal from young striker Ritsu Doan.
The 18 year-old collected the ball 20 metres from goal on a slight angle and shaped to cross, but with Galekovic committed to a ball aimed at the penalty spot, Doan let fly with a strike that embarrassed the Reds captain keeper at his near post.
Adelaide pulled a goal back when Diawara took full advantage of a slip in defence from Kim Jung-Ya to dribble into the penalty area and tee up Sergio Cirio, whose first time effort from 12 metres nestled into the bottom corner of the net.
Diawara was again involved as Adelaide levelled the score at 2-2 on 54 minutes.
The Senegalese striker provided his second assist when he laid off for Jordan O'Doherty who picked out the top corner with a first-time bullet from 25 yards - the ball still rising at is ripped into the net.
More drama ensued in the 57th minute when Ben Garuccio pulled back Oh Jae-Suk in the penalty area.
Incredibly, 37-year-old Gamba captain Endo wasted the spot-kick when he sent his spot kick high and wide of the goal as Galekovic dived the other way.
Gamba did regain the lead with a quick counter, despite Adelaide player motioning for the ball to be kicked out so Diawara could receive treatment.
Jae-Suk tore down the right flank, skipping past Garuccio his cross took a final touch off Reds defender Michael Marrone and rolled agonisingly under the body of Galekovic.
With injury time ticking away, there was to be one final twist with Diawara getting a well-deserved goal.
The Reds forward rose highest from a Garuccio free kick to loop a header into the back of the net to grab a share of the points.