Which Asian countries have adopted the Chinese culture so much that they can be called Outer China?

Which Asian countries have adopted the Chinese culture so much that they can be called Outer China? Which neighbors of China did not enter Outer China and why?

Outer China includes Japan, Korea, and North Vietnam. The countries of Southeast Asia, except for North Vietnam, and Tibet became Outer India, and the peoples of the Great Steppe created a special nomadic civilization.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.