Japan is more than 3.7 times larger than South Korea. Area of Japan - approximately 378,000 square kilometers Area of South Korea - approximately 100,350 square kilometers
Japan is more populated than South Korea. Japan - 126 million (2020) South Korea - 51.8 million (2023 estimate)
South Korea is more densely populated than Japan. Japan - 330-340 people per square kilometer (2020) South Korea - 510-520 people per square kilometer (2023 estimate)