It's called bleeding/bleed through whatsoever. If you are using a flatbed scanner, try to put a blank hard white(or maybe black) paper on top or underneath the other unscanned side, that might help.
I mean I've been waiting to see this here for years and then we get what appears to be the rough sketches rather than the finished product. I know because I've seen a handful of the clean pages before and they do not match this.
@dashat I just happened to find it online and jumped at the opportunity to buy it.
In all honesty, it may not be the completed work. It does seem like sketches, but on the other hand it seems to have all of the pages the completed work would have. I've seen those sample pages as well, and these pages are certainly far from "finished" by comparison. It is a staple-book, but I figured that was because it was (or so I had heard) self published. Perhaps the afterword could shed some light, but I don't read Japanese so I can't say.
@Lord of Evil Thank you for the tip; that would certainly fix it, especially considering every two pages is simply one larger page folded over. If I had noticed it before I finished I could have stuck a piece of cardstock between the pages. I may (no promises) go back and rescan it at some point.
@Malob: You're right, this isn't the final version. The first lines of the afterword are: "First, thank you for buying this book!!! And then, I'm sorry it's just sketches... I'll definitely finish it, sorry!"