Donghae and Yoona, were inseparable. To them, the most important thing is each other. They depend on each other like a person does to air.

Then here comes Lee Hyukjae, disrupting the balance between them. Gradually, they realize that the bubble they’ve been living in all this time isn’t really as strong as they think it is. That air isn’t the only thing they need to live. Do they really believe they were meant for each other? Or were they just ignoring the people that they were destined to be with all this time?