Kim Minseok is a quiet person. He is also the oldest prince out of his other two younger cousins. But he won't ge the crown, Junmyeon - Suho - will. He is handsome, but his youngest cousin, Jongin - Kai - is much more better looking. Kim Minseok has always been overshadowed since the day of his birth. Never gaining the interest of anyone besides his family and friends. That is, until one day he recieves an anonymous love letter declaring their love and a surprise invitation to the party event of the year. 

He has seven letters to figure out who is writing him such beautiful letters. He already recieved one, will he find out before it's too late?