虫子

The white worm who obeys Grimoire's commands. She is very protective of her master and clings to her affectionately to Grimoire's chagrin. After consuming the four treasures gathered by the other characters in response to Kagura's challenge, she assumes human form but retains her gluttonous worm aspect. Grimoire's command of worms is really because of Mushiko.

 The white worm who initially consumes Iris, she helps Iris stay alive and creates an affectionate bond with Grimoire, which is generally one-sided as the latter tends to hit out at her when she gets excessively clingy and only views Mushiko as a tool for her ultimate goal. 

Mushiko gets jealous of Tale's achievement in creating a stable story world and is driven insane to the point where she swallows Tale's diary and then goes on a rampage in the Great Library devouring entire shelves of stories to increase her strength. She threatens to make her way to the wellspring of imagination, but is eventually stalled by Historia, Shiori and Eito giving Grimoire enough time to pacify her and expel the consumed books. 

Mushiko's constant devouring of story pages apparently allowed her to evolve into a story character in her own right, which allows her to co-exist together with the other Library denizens as a character in Grimoire's world. Although she is exorcised of her worm aspect, she remains gluttonous and retains the ability to detect worms which surpasses even Historia. After joining the library, her mental state is the same as Tale's when she was just awakened, so Mushiko is allowed to work at the Great Library both to mature as a character and to atone for her past misdemeanours. /