based on the spoilers i read she really died and come back to korea, on the other hand I don't know if she died by disappearing by the potion the demon king gave her, the mc tried to kill everyone in the kingdom(probably started a war?) to make a deal with the demon king, the deal being to bring back clea back. the only thing that wasn't cleared by the op was that if the original clea came back or our mc
From what I remembered as per the spoilers I had read,
Our MC died and go back to Korea, letting the original owner of MC's body to revive(I think) and since MC and the villainess personalities are so different, the ML would see it as clear as day, that's why he will do anything to get MC back to his world.
Something like that
Anyone have a spoiler at the time when clea needs to disappear/ time ran out