누구랑 왔어?

The line, explained

The male lead walks into a party, spots her across the room, and notices she is not alone. He strolls over, hands in pockets, and asks as lightly as he can: 누구랑 왔어? Who did you come with? Everyone watching knows it is not light at all. This tiny jealous question is a perfect way to learn 랑, the casual word for with.

누구 means who. It is one of the first question words to learn, along with 뭐 (what), 어디 (where) and 왜 (why). Attached to it is 랑, which means with when a verb follows. Because 누구 ends in a vowel, it takes 랑. A word ending in a consonant takes 이랑 instead, so friend is 친구랑 but younger sibling is 동생이랑. The extra 이 just makes it easier to say.

랑 has a twin: 하고. They mean the same thing and are equally casual, so 누구하고 왔어? is just as natural. The handy thing about 하고 is that it never changes, vowel or consonant. Many speakers lean toward 랑 when talking to close friends because it sounds soft and playful. Both also mean and when you put them between two nouns: 너랑 나, you and me.

왔어 is 오다, to come, in casual past tense. The stem 오 meets the past ending 았어 and the vowels melt together into 왔어, wa-sseo. There is no separate question form here: the rising tone at the end is what makes it a question. Said flat, 친구랑 왔어 is the answer, I came with a friend. Said rising, it is the question.

The drama answer that ends the jealousy is 혼자 왔어, I came alone. The answer that makes it worse is a name. You can play with the line by swapping 누구: 친구랑 왔어? asks if they came with a friend, and 엄마랑 왔어? asks if they came with Mom. Add 같이 (together) after 랑 for extra warmth: 나랑 같이 가 means come with me.