The King of Pigs(2011)

After his business goes bankrupt, 30 something Kyung-Min (Oh Jung-Se) kills his wife impulsively. Hiding his anger, he seeks out his former middle school classmate Jong-Suk (Yang Ik-June). Jong-Suk now works as a ghostwriter for an autobiography, but he dreams of writing his own novel. For the first time in 15 years they meet. Kyung-Min and Jong-Suk both hide their own current situations and begin to talk about their middle school days.

At their middle school, they were classified by their wealth and grades. Kyung-Min and Jong-Suk were at the bottom. They were called pigs. They were bullied by a ruling class called dogs. When they were called pigs they got angry, but couldn't do anything against the dogs. Then a king of pigs appears - Chul (Kim Hye-Na). Kyung-Min and Jong-Suk became to rely on Chul-Yi.

Now, leading Jong-Suk to their middle school grounds, Kyung-Min discloses the shocking truth to Jong-Suk of what happened 15 years ago.

(Source: Asian Media Wiki)