A region that is Taiwanese territory but effectively within the Chinese sphere of influence

This is Kinmen County, Taiwan.
As you can see, it is located far from the main island of Taiwan,
and is right in front of Xiamen, the largest city in Fujian Province with a population of 5 million.

Xiamen as seen from Kinmen
Most island residents take boats to Xiamen for urban life.
Many also head to Xiamen for university or work.
It was originally part of the Xiamen metropolitan area in the past,
but after the division, exchanges were cut off. Once exchanges between the two sides reopened in the 90s,
most people now travel to Xiamen.
Because of this, the Democratic Progressive Party has been wiped out politically,
and it is an area where the Kuomintang receives overwhelming support.