Maybe Karen, I guess we'll see in the long run
Waterballoon, it doesn't have to be that complicated either. Just simply put, Ayu isn't as popular as she used to be and physical album sales in general are on a decline. Less promotion, recession, they can all be excuses but even if those things didn't happen, she probably would have sold around the same amount.
That top 50 albums list kind of goes to show that physical album sales have been steadily declining. There are the few top artists like Mr. Children or EXILE that aren't affected by it but everyone else's have been going down. It makes sense, people would rather digitally download the albums for cheaper than pay for a physical album. The world going digital makes CD sales obsolete, and other things too.
Like streaming websites such as Hulu, where you can watch shows on your computer whenever you like rather than having to watch it on TV on its airing time (unless you have TiVo). You see a lot of TV shows now having less viewers but most of the time its because the networks don't count digital viewing on streaming websites. Why buy CDs or watch TV shows on a television when you can do everything through a computer now?
I think if NEXT LEVEL was released around the same time as GUILTY, it would have better sales because imo NEXT LEVEL is the better album. But as for now, it likely won't reach GUILTY sales, but its reached the standard for present day physical sales.