HONG KONG — Marcus Lau was born in 1996, but his argument for Hong Kong’s independence from China goes back to 1984, when Britain agreed to return its colony to Chinese rule without admitting a third party — Hong Kong itself — into the negotiations.

Less than two decades since Hong Kong’s transfer, in 1997, Mr. Lau says that he and many other young people have lost confidence in China’s promise to maintain Hong Kong’s civil liberties and way of life for 50 years under a “one country, two systems” formula. Instead, he said in an interview on Thursday, China has “meddled” in Hong Kong people’s affairs and has denied them the right to a greater say in the election of their leader, the chief executive.

Mr. Lau said that he and other young people in Hong Kong had come to see themselves not as Chinese, but as belonging to a distinct Hong Kong identity. If people ask him whether he is Chinese, he said, he says no.

It was for this reason that Mr. Lau and 12 other students at Hong Kong University called in the latest issue of the student magazine Undergrad for Hong Kong to declare independence in 2047. In their manifesto, which was released online on Sunday, they cited the Chinese government’s resistance to allowing greater democracy.