Who formulated the principle that involves the country that is hostile to "mainlanders"?
Hong Kong–Mainland China conflict:  Increasingly, these tensions have resulted in a rising sentiment in Hong Kong of hostility to "mainlanders" and resentment at a perceived trend towards assimilation and interference from the mainland and the central government, and at the same time a rising sentiment in mainland China of bewilderment and resentment at assertions that Hong Kong is, and should remain, different from the mainland in terms of political system, culture and language. One country, two systems: "One country, two systems" is a constitutional principle formulated by Deng Xiaoping, the Paramount Leader of the People's Republic of China (PRC), for the reunification of China during the early 1980s.
Deng Xiaoping