maybe but it does count as a backstory aswell as getting to know the mc and seing them develop when they get in the actual world.

You can do that in many different ways, there are reasons why the original one already started with the game ending, for a good FF about Overlord you should always stick with that, I've never ever seen a good novel about Yggdrasil, why? causa no one cares.

The author should follow the original, introducing them as they appear (the new things/people/etc) also using flashbacks and extras (like auxiliary chapters/images)

Romance?

Multiple NPC from LOL, GI and like.

So it’s harem?

technically ppl do care when ever the author is asked about doing the game part , the majority always shuts towards the wanting to read the game part . In fact i have even seen the author write a compelling story about the game part of overlord it's so good atimes it can pass as it's own anime

the minority does

and how do u know u aren't part of the minority

just read the comments

????? i went through comments of every overlord fanfic i read and known of them ever minded the game part of overlord

i can say the exact opposite

You can also see that by my review being the most liked, if people didn't agree, why would they like?

your post was liked by only 7 ppl in 3 months

but it is still top 1