The puzzle consists of five poems by the famous Chinese poet Li Bai (or Li Po). In each of the poems, there are erroneous characters. These characters lead to the solution. (Clues in the flavortext: "big 5," which refers to a coding scheme for Chinese characters; a well-known poem by Li Bai has him drinking wine with the moon and his shadow for company.)
The correct characters give "white emperor city's province name"--where "white emperor" is the name of the city BaiDi (which, though in the Chonqing Municipality that was formed in 1997, is still located in Sichuan Province).
The substituted characters spell "country language net horse spell sound," which is to say Chinese (country-language), Rome ("luoma"), phonetically. Together these are a commonly used romanization system in Taiwan, and using this style of romanization gives the proper spelling of the answer, which is SZECHUAN.