Twin sisters, Arisa and Tsubasa, are separated by their parent’s divorce. The twins secretly exchange letters with each other during their separation. They are finally united after three years and Arisa asks Tsubasa to pretend to be her and spend a day in her school just for fun. At school everyone seems very nice to Tsubasa (who is pretending to be Arisa) and everything seemed normal – until she finds a strange note in her sister’s shoe locker.