One day in the Korean high school, there is a girl named Kim Moo Na. She has an older sister named Kim Moo Hyung. Moo Hyung knows that Moo Na has no friends because she is deaf mute. So, Moo Hyung always gets on with Moo Na. On Moo Na's birthday, Moo Hyung gives her a small note so Moo Na can write everything what she wants to say. Then, she writes on the first page.

I fall in love with Onew, the popular guy. Please keep this a secret.