System: I Have Become the World's Substitute Teacher

Song Liang was lured into another world by an unscrupulous system, but Song Liang never expected that the system would ask him to do such a thing. What? The unscrupulous system wants me to study in an academy? What? The unscrupulous system actually wants me to teach for other students? What? The unscrupulous system wants me to become the king of substitute teachers? .... Many years later. What? I, Song, want to save the world? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.