Arisue Rio firmly believes in the principle that "the outside is the most important." When she says that to male nail technician Irima Yoshitsuki, he puts a specially made, cursed gem on her nails and told her: "If you kiss a boy you don't like, then time will rewind."
Rio didn't believe it; but after being confessed to by a super cute kouhai, they started dating and even kissed! After they kissed, time rewinded to the day before?!