If you want the fullest picture of 'I Have to Be a Great Villain', I’d start with the original prose source — that usually means the
web novel or light novel entries. Those versions give you the internal monologue, pacing, and worldbuilding that adaptations compress. Reading the original first helps you understand why characters act the way they do and catches little world details that manga or anime sometimes skip. I’d read them in publication order: volume 1, volume 2, and so on, including any official short story collections or bonus chapters released alongside volumes, because those often expand side characters or explain motives.
After finishing the core prose, move to the manga adaptation. The manga is a great way to re-experience scenes with visual flair — expressions, panel rhythm, and occasional extra scenes that weren’t in the main volumes. Treat the manga as an enhanced retelling: it won’t usually replace the novel’s depth, but it can correct pacing or add emotional beats that hit harder once you already know the plot.
Finally, if there’s an anime adaptation, watch it after the novels and manga. Anime tends to streamline or reorder parts for runtime, so seeing it later lets you appreciate the choices and note what was condensed or changed. Sprinkle in side materials (volume extras, drama CDs, author notes) as you go. Personally, doing it in that order — novels, manga, anime, extras — made the characters feel richer to me, and I kept finding little touches in adaptations that made me smile.