What is the capital city of Japan?

Tokyo is the capital city of Japan, making it the correct answer. As the political, economic, and cultural heart of Japan, Tokyo is a vibrant metropolis that plays a central role in both national and international matters. It is home to the Japanese government, including the Emperor's residence, and hosts numerous cultural landmarks, businesses, and a diverse population.

Seoul is the capital of South Korea, while Beijing is the capital of China, and Bangkok is the capital of Thailand. Each of these cities is significant in its own right, but none are the capital of Japan. This distinction clearly establishes Tokyo as the accurate answer to the question about Japan's capital city.