HONG KONG — He has been locked up for more than a year in a secluded island jail, but the bespectacled 28-year-old inmate, Edward Leung, is the closest thing Hong Kong’s tumultuous and leaderless protest movement has to a guiding light.

He coined the protesters’ most widely chanted and, for China, most subversive slogan; he helped pioneer some of the movement’s rougher tactics; and he gave voice to the idea at the heart of Hong Kong’s struggle, now in its 10th week, to avoid becoming just another Communist Party-run Chinese city.

The protests were ignited in June by anger at plans by the Hong Kong government to allow extradition from the former British colony to mainland China. And they have been freighted since with a host of other complaints about prohibitively expensive housing, unfair elections and alleged police brutality.

But at the movement’s root is a dramatic shift in identity since Britain pulled out in 1997. The increasing influence of the Chinese government on the territory in recent years — what the protesters see as encroachment — has galvanized a large majority of Mr. Leung’s generation to reject ties to mainland China and fiercely assert what a growing number see as a distinct and entirely separate identity.