I think it stems from JNs that have different covers for each volume released; it gives hints of what will happen in the next volume while also giving some freshness to the look of the story.
Saying that, it isn't a necessity.
You can change the cover whenever you want to - if you do at all.
Saying that, it isn't a necessity.
You can change the cover whenever you want to - if you do at all.
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