Demon King Teacher

Wang Bu'er, an extremely cowardly undergraduate, entered a prestigious high school by chance as a mathematics teacher and head teacher. Unexpectedly, the class he taught was a veritable death class. Faced with all kinds of difficulties from the students, Wang Bu'er suffered a series of blows. Just when he was desperate, he was knocked unconscious by a Cadillac. When he woke up, he suddenly found that he had restored the memory of his previous life, and his previous life turned out to be a big devil... Who was he harmed in his previous life, and how should he take revenge?