I don't understand Korean wedding ceremony correctly. I thought, she's not married because the groom's run away…
I'm Brazilian but I've watched "wok of love" and there's a situation like that. I think there's an official registration. In Rara's case, I think that was a strategy to garantee the relation between families.
Some OSTs are powerful! Reply 1988 and Crash Landing on You have a warm place in my heart <3 But I have to agree with you that Itaewon Class's OST walks side by side with the story and make it more incredible!