Water.
The waterway that separates Taiwan from mainland China is the Taiwan Strait. The capital of Taiwan is Taipei.
It is known as the "Sea of Japan," though Korea in particular would prefer it be known as the "East Sea."
If the three main southern islands you are referring to are the Ryukyu Islands, including Okinawa, and the rest of Japan referring to the 4 main islands of Japan, then the answer is the East China Sea. If the three main southern islands you are referring to are Kyushu, Shikoku and Honshu, and the rest of Japan referring to Hokkaido, then the answer is the Tsugaru Strait.
Bass Strait separates the mainland of Australia from Tasmania
Korea was part of China until 1895. Traditionally, Korea thought China as a parent or big brother country, and China treated Korea as a son country. After 1945, It still continue between North Korea and China. For South Korea, China is two of main countries influencing South Korean politics with U.S.
North Korea, South Korea, The United States and I think China. Hope this helped :D
China - MandarinKorea - KoreanThailand - ThaiJapan - Japanese
Main landmark is The Great Wall Of China.
Japan has no bordering countries since it is made of islands. The five closest countries to Japan are (in order) Russia, South Korea, North Korea, China, and Taiwan. North and South Korea, Russia and China.
Geographically speaking, South Korea is the southern half part of Korean peninsular. So it borders only with North Korea. North Korea borders mainly with China and also with Russia. Japan is located eastern side of Korean peninsular. From Japan, high seas exist, although very close. Western side has China main land with high seas between them.
Historically, China has been the main influence in Korea. Today, South Korea is mainly influenced by English.
The body of water that separates the three main southern islands from the rest of Japan is the East China Sea.