Chaeyoung's quiet high school life gets turned around when her single father remarries, to a 30-year-old woman named Myoui Mina. Chaeyoung doesn't like her new stepmom at first, but things don't stay that way for long.

Where Sana is Tzuyu's stepsister, and Mina is Chaeyoung's stepsister... A bit different from the one shots