When Sawoo gets bullied in high school, his only friend Kido promises to teach him how to become the greatest villain.
But Kido goes overseas after teaching Sawoo only two of the three rules.
Faithfully following the two rules, Sawoo writes Kido many letters in the hope that he will get to learn the last remaining rule but Kido never replies.
One day after four years, Kido shows up in front of Sawoo, thinking those were love letters.

Original Webtoon:
Ridibooks, Bomtoon, MrBlue, Lezhin

Official Translation:
Japanese, Vietnamese, Spanish, German
English: Pocket Comics, Lezhin, Manta
French: PocketComics, Bontoon
Thai: WeComics, Boomtoon

Note: The English translation by Netcomics was put out digitally in 11 chapters (complete); it was also printed in a single volume (however, the printed version doesn't contain the 11th chapter.)