인싸 /in-ssa/
Popular insider / Social butterfly
Short for 'insider' — a socially popular person who fits in everywhere and is always in the loop on trends. The opposite of 아싸 (outsider).
Examples
걔는 어딜 가도 인싸야
She's the life of the party wherever she goes
인싸들이 요즘 다 저거 듣더라
All the popular kids are listening to that these days