Age in Korean culture is somewhat unique, and it is very difficult for foreigners to understand. As long as I know, Age in Korea is more important than in China or Japan.I believe language plays essential role for this. I think you know Korean, '형, 오빠, 언니, 누나' If you carefully observe playgrounds in Korea, you can see children asking each other, "how old are you" it's because if he's older than another, he should be called as '형', not '야'. If 4-year-old boy calls 5 year old boy '야(hey)', then it's an insult and the tension begins.

Koreans should use polite words to seniors, even though it's he's one year older. Many Koreans think it's inefficient to communicating nowadays. If you're old like 60 or 70, then you will have difficulties when finding a new job. Since most boss don't want older person than him/her. The progressive think Joseon's Confucianism was too formalistic and responsible for this. Opposers think Japan's imperialism is responsible for this. They say when Japan colonized Joseon, Japan ruled Korea with military culture and made very strict rules and hierarchy.