For honorifics, age and gender are most important for determining how formally you should speak. The age of the person you are speaking to determines the specific endings you would use for verbs. For this reason, it is not considered rude to ask someone for their age! From my experience, many people are flattered when you guess their age is a lot younger than they actually are! People generally think I am 26 years old when I am actually 22. I think they are 24 or 25 when they are really 32!
Since Korea is a Confucian-based society, social order and respecting elders is embedded in everyday life. This affects the way people interact with each other. Being the youngest in the group (maknae) means that you would have to do whatever your elders told you to do. The youngest must be polite and hospitable, which means they have to take care of everyone's needs. For example, the youngest would have to fill everyone's cups with water or tea, and make sure that their cups are always filled.
Traditions like this have a big influence on social dynamics in a group! Due to this tradition, a lot of my Korean friends will tease the youngest in the group. In the most traditional setting, a one-year difference would make the older person more superior. However, the new generation is becoming more modern and Westernized, so they do not hold strict formalities with people in different age groups at the same school.
What’s interesting about honorifics is that, even if you are one year apart, you cannot be considered to be friends.
