I'm not entirely sure as I haven't read it in detail. But generally, it might be about a character who decides to stop being a hero. This could involve things like the character being tired of the hero life, facing moral dilemmas in heroics, or having some personal issues that make them want to quit.
The 'I'm Quitting Heroing' light novel might be a tale of self - discovery. The protagonist, who was once a hero, realizes that the concept of heroism they once adhered to is not as straightforward as they thought. There could be political or social aspects within the story that influenced their decision to quit. For example, they might find out that the system they were part of as a hero was corrupt or using them for ulterior motives. This realization then leads them on a journey to find a new purpose in life, away from the hero identity.