what is that mean ? in her thigh there is something
I only just recently learned that these are the Japanese equivalent of 'tally marks'. Like when we are recording a count, we make four vertical lines as we count, and then one slanted line to bind them together to show a count of five. Each mark in these 'characters' is used to tally a count.
In truth, compared with 'bundled' lines like we use in the West, these look overly complicated, but it's what you can sometimes see in school anime where they are counting votes for 'what will we do for the Culture Festival' thing.
EDIT: Hahahaha! OK, it's all explained in the translators notes at the end. Ha! That's what I get for 'turning pages' too fast.