Do Kyung Soo of the band EXO has fallen in love with a girl during his childhood. While growing up, his love for her grows more and more. But one day, when they are both all grown up, ready to face the world, Kyungsoo finds himself in trouble. Will he be able to find his love again? Will they be able to meet again? Most importantly, will he remember her? Kyungsoo and his first love make a deal at the age of 5...something tears them apart during college. And death knocks on someone's door.