Masamune-kun's Revenge

is a manga series written by Hazuki Takeoka and illustrated by Tiv. The series is published by Ichijinsha in Japan and by Seven Seas Entertainment in the United States. An anime television series adaptation by Silver Link aired for 12 episodes from January 5, 2017 to March 23, 2017.

Plot
As an overweight child, Makabe Masamune was mercilessly teased and bullied by one particular girl, Adagaki Aki. Determined to one day exact his revenge upon her, Makabe begins a rigorous regimen of self-improvement and personal transformation.

Years later, Masamune re-emerges as a new man. Handsome, popular, with perfect grades and good at sports, Masamune-kun transfers to Aki's school, and is unrecognizable to her. Now, Masamune-kun is ready to confront the girl who bullied him so many years ago and humiliate her at last. But will revenge be as sweet as he thought?

Official

 * Official anime website (in Japanese)

Other Sources

 * Manga
 * Anime
 * Anime