Many Koreans consider the rising sun flag a throwback to Japan’s imperial system and militarism during its World War Two expansion into Asia.
On the same day, a player found that one of the game’s artificial intelligence bots was named “Unit 731” by the developers.
Unit 731 was a division of the Japanese army which developed chemical weapons, and conducted human experiments on Chinese, Korean and Russian prisoners of war. 10,000 people died in its testing facilities.
The company said the AI bot’s name would be removed from the game, and the pilot’s mask was not supposed to be released to players.
It promised to scrutinise items before they went on sale in the future.
“We apologise for causing concerns over a pilot mask item,” the company said in a statement.
“We will conduct an overall re-examination of our image production process to prevent such a recurrence.
“We will enhance procedures to scrutinise game items before their release and hold the person in charge responsible.”