in a world where you are born with 5 luminous hearts inside your wrist. When your heart is broken in some way, one of the hearts loses its color. Once all hearts have darkened, it is said you will never love again.

beomgyu is a music student who has only one heart. He promised never to fall in love again. That changed when Taehyun, a boy with 5 full hearts, arrived.

"How much do I bet I can turn off one of that boy's hearts?"

said to his friend soobin. out of spite he bet. soobin just told him that he's crazy.