Here are Korean expressions for "have a crush on someone" and other related ones.
- 그에게 반하다: Have a crush on him - most common and traditional.
- 그에게 꽂히다: Have a crush on him ("He's stuck on my heart") - newer, slangy.
- 그를 좋아하다/사랑하다: Like/Love him.
- 그에게 호감을 가지다: Have a soft spot [favorable feelings] in one's heart for him.
- 그에게 (마음이) 이끌리다: Be attracted to him.
- 그에게 홀리다/혹하다: Be (temporarily) infatuated with him (usually negative).
These words usually describe one's sentiment to a third person, just like "have a crush".
These phrases can be used in any situation, but they are just plain descriptions with no romantic feel.