The last man of Hong Myung-bo's World Cup squad joined the team for training in Paju, Gyeonggi Province on Sunday.
Yun Suk-young was unable to leave Queens Park Rangers until the club's game against Derby County over the weekend in the race for promotion to the English Premier League.
Yun went straight to Paju as soon as he arrived at Incheon International Airport on Sunday.
Korea will face Tunisia at 8 p.m. on Wednesday for their last international friendly at home before the World Cup.
"The players are not in peak form yet but we will try our best to win against Tunisia as it will be our last game in front of Korean fans at home ahead of the World Cup," said Hong.
The team will leave for Miami, Florida on Friday for overseas training before going to Brazil.