Greatest Villain

When Sawoo gets bullied in high school, his only friend Kido promises to teach him the three rules to become the greatest villain. But Kido goes overseas after giving only two of the three rules. While faithfully following the two rules, Sawoo writes Kido numerous letters in hopes of receiving the third rule, but Kido never replies. After four years, Kido comes back believing Sawoo has been writing him love letters.