I'm sorry, but South Korea has every rights to not be okay with Japan waving the 'rising sun' flag with pride.

That flag is HEAVILY grounded with Japan's imperialistic and militaristic past, as well as with Japan's EXTREMELY brutal occupation of Korea during WW2. I know the flag technically predate WW2 by 40 years, but it has been widely used during that period. Like it or not, the rising sun flag is a symbol of Japan's imperalism now. The swatiska also predate nazi germany, yet you wouldn't try to wave it during Olympics, would you?

from my visit to South Korea and china I learned that past japan have been major dicks to both, maybe more so to Korea than china.

the ol' classic of assassinate a queen, put a puppet king on the throne and burn down a lot of castles.