"Graphic Quality Issues

Stock customers expect commercial quality assets for print, digital and merchandise use.

IMO, these are too pixelated for Stock.

You might try submitting these to other services that specialize more in anime.

Illustrations such as these are always difficult when it comes to determining specific reasons why they were rejected. That said, there is a good deal of noise and grain, and some slight under- and over-exposure in specific areas. Adobe will often reject assets for this reason. It also lacks overall sharpness when viewed at 100%. But again, where do we draw the line on such matters when it comes to playful illustrations? That answer remains up to Adobe moderators. I suspect that other stock sites would accept this type of material, but Adobe stock works by its own set of rules. These images have a place somewhere, but probably not on Adobe Stock.