Mochizuki's Musings are a small author's note by Jun Mochizuki on the beginning cover flap of each volume of Pandora Hearts. Often they display Jun as a cat being traumatized in some way by one of the characters from the series, though more specifically, by one of the characters who were a main focus in the volume, as well as a small amount of text that refers to something in Jun's life. These images are in full color, drawn in chibi-style and are meant to be amusing for readers.
Jun-Cat is a chibi cat that represents Jun Mochizuki so she can interact with the characters of her Volumes during the illustrations in her Musings. Jun-Cat appears as a black cat with white eyes almost always expressing her fear and distress as "!?", and a pink mustache, which in two separate omakes, Leo has asked if he could rip it off.
Jun explains that she thought youth was reserved for teenagers but when she looked it up in a dictionary it was defined that it extended all the way to the age of twenty-five. This made her want to roar like a youth forever, that's how she felt.
Jun talks about often going to a convenience store after becoming a Mangaka and befriending a middle-aged woman, who now gives Jun a free oden whenever she goes in to buy some. Jun remarks on how nice her friend is.
Coupled with this is a picture of the Jun-Cat, who had apparently been painting when B-Rabbit sat down and asked if she was calling B-Rabbit stupid. To prompt an answer out of Jun-Cat, B-Rabbit stabs her with a paintbrush, calling Jun a bum.
Jun writes that the fact that her new cell-phone often vibrates on its own scares her, and so she wonders if it's the grudge of her own phone after it had died when Jun dropped it in her coffee.
The image with it shows Alice carrying B-Rabbit's scythe over her shoulder, with Jun-Cat tied up and hanging upside down from the end of the scythe.
Jun writes that she's uncomfortable using computers, but had finally bought something online and was happy with how easy it was, though it was apparently too easy as her room will soon be over run with reference texts. Jun mentions that she'll have to but a bookshelf online next.
The image is of Jun-Cat distressing, as usual, about Vincent Nightray's thirst for blood as he decapitates a toy rabbit with his scissors.
Jun writes about how she came to realize one day while working that it was a miracle that she was able to draw manga for a living. Jun was feeling grateful and thanked her assistants for supporting her. They apparently told her that she was being creepy.
The image with Jun's Musing is of Cheshire hissing at Jun-Cat, who tells Cheshire that she's sorry for making him suffer so much in the manga.
Jun writes that Volume 6 had the most girls ever featured in it as there were so few in Volume 5, and though there were a lot of characters together in the Volume, Oz is still the main character. Jun then "tells" Oz to do his best.
Jun-Cat is shown feeling guilty as Fang and Dug turn their backs and become depressed. Jun-Cat tells them that she can't help if they're not on the cover, and subtly adds that if they were, no one would buy the volume.
Jun writes that her two neighbors bring her meals now a-days, which she loves because in modern Japan you don't associate very much with your neighbors. Jun says that the food was delicious, and that she draws the manga with the support of her neighbors.
Rufus Barma (illusion) recites, "The great fool who hath mistaken Nichola (Star) Cage for a TV drama in which a detective named Nichola (Star) is the hero and thou art one in the same, is that not so?" Jun-Cat mentions that life without coffee is unthinkable, and asks Rufus how he could know such a thing, distressing as always.
Jun writes how she would love to go to Great Britain that year along with anywhere else in Europe like Italy, France and Germany. Jun says she'd like to immerse herself in fantasy worlds and that just imagining it makes her very happy.
Jun-Cat is shown distressing with papers flying all around her.
Jun writes that she and her assistants check every volume multiple times yet they can never get rid of typesetting errors. She calls them formidable enemies that they tend to ignore the more serious they are. She says that it's terrifying.
Jun-Cat is shown crying as Elliot Nightray has her pinned down with his foot while yelling at her asking her if she had no shame for still having typesetting errors even after all her assistants look over the volumes.
Jun writes two stories from her friends: One friend had taken a long vacation to finally go to Great Britain, explaining how wonderful she though Edinburgh was. The other explains that they had recently gotten married, and because of their spouse's work, they'd be relocating to London within the next year - which worried them, but their heart was filled with hope.
Jun-Cat is shown with Sharon Rainsworth about to hit Jun-Cat with her harisen, asking when she will appear in the manga, whilst Jun-Cat hides under a nearby pillow.
Jun writes about how some of her readers had sent her emails because they were extremely confused by her comments in the Mochizuki's Musings of Volume 10, explaining that she's sorry and that she won't be able to leave Japan for quite some time. She the declares that she will go abroad in the following year, saying that she's not declaring that she won't be able to go, again.
Jun-Cat is shown to be panicking as Leo comments on how he's never seen a cat with a pink mustache and how he wonders what her insides look like.
Jun explains that she felt as though she had drawn with the greatest sense of calm up until recently. Jun mentions how she had never felt the urge to break down in tears from the story before, claiming that she's reached the juncture of the plot and that Volume 12 is just that, thanking readers for reading.
Jun-cat is distressing as Marie pushes her to the ground and holds her there with her foot, as she questions how Jun could dare behead Rytas.
Jun explains that she's finally stepped on foreign soil, managing to defy her weak-hearted comment in Volume 11. Apparently, things had been very comfortable abroad, making Jun want to return to Paris, or live in Chatsworth, but she now knows that miso soup is the soul food of all Japanese people because of her adventures abroad.
Jun starts off by talking about her like for clocks. She mentions that she prefers analog to digital clocks, but loves antique clocks even more than standard analog clocks. Her heart apparently flutters whenever she sees a wind-up clock, loving the selfishness of the wind-up clock. Jun even compares it to a child, capable, but automatically stops and pouts if she ignores it. Jun also mentions that she finds the winding sound of the wind-up clocks to be lovely, asking if her readers feel the same.
Jun-Cat is shown distressing as a clone of Humpty Dumpty put's Jun-Cat's head in his mouth and lifts her off of the ground.
Jun complains how the studio that she's been renting since her work on Volume 6 was finally getting cramped. Jun expands on this, stating that she has so many books that they're piling up everywhere, and she no longer has enough room to add a bookshelf. Jun wants a large library, like the ones that aristocracies have; noting a love for e-books as well, but explaining that she feels more 'at home' with a lot of books stacked up everywhere.
Jun mentions that she only used to take showers because she thought being in the tub was a waste of time since there's nothing you can do while you're in there. But lately she's began reading in the tub, and so she thinks that she's more at ease with taking long baths because of it (although she's not sure); adding that she's beginning to make her way through the reference books she has piled up.
Jack picks up Jun-Cat, calling out for Glen Baskerville and claiming that he'd found a rare cat with pink whiskers, becoming more over-joyed when he finds out that Gilbert Nightray and Vincent are with Glen as well. Meanwhile, Jun-Cat struggles, and panics, not knowing what to do.
Jun-Cat is shown to have been wrapped up in bandages and is being held by an overjoyed Levi.
Jun-Cat is shown to be distressing in the hands of Miranda Barma, who is carrying her severed head.
Reim Lunettes is shown to have lost his glasses, stepping on Jun-Cat's head whilst searching for them.
Ada Vessalius is shown in her witch-garb, reading from a spellbook whilst Jun-Cat sits in a boiling pot beside her, fearing for her life.
Oswald is shown sitting on Jun-Cat.
Gilbert is terrified of Jun-Cat.
- Jun-Cat's pink mustache was not present on her face in the first and third Mochizuki's Musings for an unknown reason, whereas in all other appearances, her mustache is present.