Dear Boy(2014)

Dear Boy

A story of bitterness, hate, and revenge... Callous to the pains of his classmate being bullied by punks, Yongju one day finds himself the target. When Yongju's attempt to get back at the bullies goes terribly wrong, his brother Yongjin pledges to enact justice - setting him on a methodical yet twisted path bent on ruthless vengeance.

(Source: Lezhin)