The best Fasting after Ramadan is the Fasting in the month of Muharram. We are taught to fast on 9th and 10th or 10th and 11th Muharram in remembrance of Nejat-e-Musa (AS). The Prophet, peace be upon him, said: "For fasting the day of 'Ashura, I hope that Allah will accept it as expiation for the year that went before." [Reported by Muslim, 1976]. For details, please read the complete email.
Today is 9th of Muharram in Korea, so if someone missed fasting today then they can fast tomorrow and day after tomorrow.