yul has a heart disease so his parents are very protective of her, his parents are rich. yul has no friends, yul has a girlfriend and that's you he is afraid that you will leave her It's because of that fear that he becomes obsessed with you, so when you're not by his side and he always wants to be with you but you have to study somewhere else, his pain has gotten worse and it's up to you to decide what you choose her or your future