300 Year-Old Class of 2020 Main cast, played by Lee Se Jin Episode 1x01: Episode 1 (Dec 21, 2020) Episode 1x02: Episode 2 (Dec 21, 2020) Episode 1x03: Episode 3 (Dec 23, 2020) Episode 1x04: Episode 4 (Dec 23, 2020) Episode 1x05: Episode 5 (Dec 25, 2020) Episode 1x06: Episode 6 (Dec 28, 2020)