Lee Jinsook is a curious girl. She knows everything: which kind of book Sojung read when she's sad, the way Cheng Xiao frowns her forehead when she can't understand a korean word but pretends she does, how Jiyeon likes to fold her own clothes when she's nervous, and the many ways Dayoung likes to when she isn't well, because her fellow maknae always knows which buttons to push. She knows everything, until she doesn't. Until she learns something she never thought about: her members, her friends, had some feelings Jinsook herself never explored. Why is it that Juyeon has so many secrets? And why does Jinsook's heart suddenly want to be one of them?