One girl, two boys. They grow up together since childhood. They are orphans, have no parents. The girl is the oldest, while the boys are a year younger. But, what will you do if you end up fall in love with your best friend, that you can call "older sister" or "noona" in Korea? What if the girl you love has another boyfriend and doesn't love you as you did? What will you do if the one you love is actually suffering from a disease? That's what Choi Sooyoung and Kwon Yul are facing...

They don't know that their first and eternal love is actually a nightmare to them...