Let me be clear. There is no real way of estimating how many people have read / are reading Shadow Slave. It is also true that it is in no way shape or form as big as most numbers show. In Webnovel and the pirate sites that imitate the format, clicking on a chapter counts as a view. Which means that a single reader is enough to get the views up to 2977. If the story was just on Webnovel we could estimate around 30k real readers and that's counting people who dropped the story or re-read chapters in the numbers.
Of course, Shadow Slave is the most pirate web novel ever which makes it impossible because even pirate sites have really big views that work in a similar way to Webnovel. If I had to do a real guess I would say around 100k real readers.
That would put it around the same numbers of readership as some of the biggest Webnovels like Worm or The Wandering Inn(They might not be as popular in social media but they do have big readership numbers, they are also considerably older).
Comparing it to other Asian web novels is a little bit unfair even with inflated numbers. Using Lord of The Mysteries as a comparison point is pretty unfair because Chinese readership is big enough to inflate the numbers to an unrealistic standard. Re:Zero has like what, 16 million legal copies in circulation? Who knows how much more people read it pirated. I don't think Shadow Slave reaches those numbers quite yet, especially not without official translations and other stuff.
What do you think the real numbers are?