I am leaving Korea after living here for several years?

A farewell gathering (송별회) is the norm, and coworkers or friends will often host a meal or drinks to see you off. It's considered polite to tell your seniors and boss personally that you're leaving rather than just disappearing, and small thank-you gifts are appreciated. Koreans value staying in touch, so keeping people on KakaoTalk and sending an occasional message afterward is the natural way to keep the relationship.