After some searching through Japanese I get 伴侶(반려, ballyeo) but that's closer to companion and in Korean it's just turning up images of pets. Well there's always the obvious 인생의 파트너 -- it's explained well in many articles: https://ko.mncoa.org/life-partner-452 -- in Japanese too it's just put as two people walking the road together . . .
Or 연인 if you mean sexual partner . . .