According to the website of vidhub video library, Tang Chaoyang and Song are two villains who specialize in looking for foreign migrant workers to pull relatives, then introduce them to work in coal mines, create "safety accidents" and then exchange their lives for compensation.
Yuan had to drop out of school to work for his sister because his father went out to work late. As a result, he met the black-hearted Tang Chaoyang and Song, and wanted to trick them into "doing" underground and get compensation. So, Yuan didn't know there were people in the well.