The story starts with the theory that if we flirt with someone continuously for 21 days, there will be a chance that that person will start to be interested back and the 11 month theory is that we will be able to forget ex-lovers if we break up for 11 months. Nune likes Vicky, a customer of the coffee shop. Nune talks about Vicky to Pie(Ferin) every day, which makes Pie annoyed to listen to it. So she challenged Nune to flirt with Vicky within 21 days. Nune accepts and finds a way to flirt Vicky. Nune also challenges Pie back to forget Vava's(Great) her ex-girlfriend in 21 days. Because in 21 days, it will be 11 months. Pie accepted the challenge because she thought it very easy. But that day, Vava appeared at the coffee shop. After Vava came back, they got close and adjusted their misunderstanding.