Book Eaters

Creatures that gain the knowledge stored in writings by devouring the ink used to record them. This would leave the material/book/scroll behind, unharmed, but perfectly blank. If one was careless, this could mean losing whatever knowledge was contained forever.
It was believed that using liquid-based inks in recording/writing would attract them, and as such, it was considered poor practice to use it. Especially prevalent mythology among Unnamed, whom continue to avoid liquid inks in their writing. It was also rather common among Masuge in the time of Some Random Fucker-- he was a bit non-traditional in his choice to alternate between ink on paper/bamboo and carved bamboo slips for his writings.

Often used in teasing i.e. "Oh, don't bother with him. He's a book eater." It's taken to colloquially mean someone who greedily absorbs any knowledge they can; one who is always reading/writing and learning.

Historical Basis

hìzámạ́ had a habit of stealing the original writings from books/scrolls/etc in a very similar way-- it was to add the original copies to the library dimension, but he didn't much care for the materials used, and as such left them behind. The library dimension also has many such beings-- they are shikigami created to maintain the works stored there and find new works that do not yet exist in the library. Contrary to popular thought, these beings more often take the forms of foxes than any humanoid (whereas they are almost exclusively depicted as humanoid in media).
This practice later became stealing the original inked work and leaving a perfect replica, as to stop restricting the information mortals had access to.

In Literature

Later depictions depict book eaters as messengers of the gods.

In Art

Common images of book eaters depict them as beings made entirely of paper and parchment in a humanoid form-- taking after whatever species the artist is, usually-- and every drop of ink devoured has its writings permanently added to the ever-moving words that cover their bodies. (for a general mental image of the moving text, think the black books from Skyrim).

Date of First Recording

150