This Isn't Revenge, He Said

A spine-chilling suspense following a man hellbent on revenge. Ryukichi Kojima was a promising young man who dreamt of making it in the professional world of shogi. However, he lost everything when six of his high school classmates started bullying him relentlessly, day after day. Years later, those same bullies have become working members of society, and are living out their best lives. But in the shadows lurks a dark figure wearing a peculiar hooded mask, observing carefully. In the figure's hand, is a notebook with the name of the boy they once tormented...

(Source: MangaPlaza)