Doujins have been scanned without unbinding, resulting in skewing and some bleedthrough here and there. Work was done to try and reduce any glaring mistakes, but some things may have been missed.
Let's be real these doujins are so rare and cost a shit ton of money for each so I wouldn't mind the bleeding through. Heck last time I checked Inai Uchi's 1st Kirika doujin was like 10,000yen.