Two best friends living together for 10 years. Both know they are more than just friends, but never ever made the first move to confess to each other. For 10 years, they have tried to test each other's feeling through the songs they sang, trying to induce each other to make the first move in confessing. From Taeyeon’s 'If', 'Can You Hear Me', 'I Love You', 'Closer', 'Missing You Like Crazy', 'Love, That One Word’, to Tiffany’s ‘Stick With You’, ‘Because It’s You’, and ‘One Step Closer’, to their duet ‘Because of you’, ‘Lady Marmalade’, and ‘Lost In Love’, they used those songs to sing out how they feel, hoping to get response from each other. But no, neither of them dare to make the first move.

But then, Tiffany was invited to sing the OST of Blood titled ‘Only One’. She decided that this will be the last song to induce a confession from Taeyeon. Will she be able to succeed in getting a confession from Taeyeon, or will it be another failure that will stop this game of induce confessions?