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Brazil produced a first-half display of mesmeric attacking football to secure their passage through to the quarter-finals.
South Korea were cut apart as Vinicius Junior, Neymar, Richarlison and Lucas Paqueta all scored inside 36 minutes.
Paik Seung-ho got one back in a more even second half, but Brazil look like a team in formidable form ahead of a last eight meeting with Croatia.
It took only seven minutes for Brazil to take the lead and send their vocal supporters into raptures.
Raphinha broke clear on the right and sent a low cross into the box which evaded everyone and dropped at the feet of Vinicius at the far post. The Real Madrid man took a touch, unfazed by the onrushing defenders, before caressing his finish into the top corner.
Just a few minutes later, Richarlison nipped in front of Jung Woo-young, who in his attempt to clear the ball clipped the striker and gave away a penalty. Neymar, in typically flamboyant style, stuttered his run up and successfully bamboozled goalkeeper Kim Seung-gyu to convert from the spot.
South Korea were, unsurprisingly, rattled after making the worst possible start, but they nearly replied in stunning fashion as Hwang Hee-chan forced Alisson into a superb save with a rifling shot from distance.
Paulo Bento’s side began to commit more players forward out of necessity, but they were punished again by a ruthless Brazil side just before the half-hour mark.
An exquisite, stylish move was started and finished by Richarlison, who skilfully evaded his marker and found Marquinhos. The defender picked out Thiago Silva while Richarlison continued his run into the box, and the Chelsea centre-back played an inch-perfect through ball for his teammate to slot home from close range.
This was Brazil at their free-flowing best, and they had a fourth before half-time when Vinicius lifted a ball into the middle for the onrushing Paqueta to cushion a volley into the bottom left corner.
Korea were in danger of humiliation but continued to defend with a man-to-man approach and go forward with apparent reckless abandon. Richarlison, running into acres of space, might have made it 5-0 before half-time but he was denied by Kim.
Alisson was on hand to deny Son Heung-min as Brazil switched off and allowed the Spurs man to race in behind early in the second half.
At the other end, Raphinha twice forced good saves from Kim, but it was clear Tite had instructed his players to conserve some energy and attack with less intensity with such a comfortable lead.
That allowed South Korea the occasional opportunity, but Alisson was proving almost unbeatable, making another impressive stop at full stretch from Hwang’s powerful shot.
The Liverpool goalkeeper could do nothing about the eventual consolation, though, as Paik’s ferocious strike deflected into the bottom corner.