Belgium fought back from two goals down to beat Japan 3-2 with an added-time goal from substitute Nacer Chadli on Monday to set up a World Cup quarter-final with Brazil.
The distraught Japanese, who went 2-0 up with goals by Genki Haraguchi and Takashi Inui early in the second half, fell to the turf after Chadli poked the ball home from Thomas Meunier's cross four minutes into added time at the Rostov Arena.
Belgium, who had taken a conservative approach to the game, got back into contention with late goals by Jan Vertonghen and substitute Marouane Fellaini before Chadli struck.
"That's what happens in the World Cup. It was a test of character and a test of the team. It tells you everything about this group of players," said Belgium coach Roberto Martinez.
One of the most exciting teams of the group phase, Belgium faced an embarrassing exit but finally clicked to become the first team to win a World Cup knockout game from two goals down since West Germany beat England 3-2 after extra time in 1970.
Belgium's 'golden generation' have now scored 12 goals in four games in Russia ahead of a mouthwatering last eight clash with Brazil who beat Mexico 2-0 earlier on Monday.
With centre back Vincent Kompany back in the lineup for the first time since picking a groin strain in a warm-up game, Belgium had looked safe at the back but uninspired up front.
Both teams fought a tight midfield battle but their forwards froze in the area and Belgium's wide players, Meunier and Yannick Carrasco, did not take risks going forward, effectively turning a 3-4-3 formation into a more conservative 5-2-3 system.
Japan got closest to a goal in a dull first half when Belgium keeper Thibaut Courtois let the ball slip from his hands and between his legs but recovered before it crossed the line.
The Japanese were ahead soon after the break, though, when Haraguchi beat the offside trap and ran into the area to beat Courtois with a cross-shot in the 48th minute.
Belgium responded but Hazard's shot rattled the post and Japan doubled their tally in the 52nd when Inui picked up the ball 25 metres out and fired a missile into the back of the net.
The Red Devils were still struggling but they pulled a goal back after 69 minutes when Vertonghen looped a header from a high clearance back across goal into the far top corner.
The momentum had shifted and in the 74th, Eden Hazard's cross was met by Fellaini, who equalised from close range with a powerful header.
Belgium continued to push forward and both Chadli and Lukaku forced Japan keeper Eiji Kawashima into a couple of spectacular saves with powerful headers four minutes from full time.
In stoppage time, Keisuke Honda's 30-metre free-kick was parried away by Courtois. The keeper then launched the ball to Kevin De Bruyne, who made a beeline through the field before finding Meunier, whose cross was met by Chadli for the winner.
