Sabitsuki

Appearance
Like Madotsuki, here eyes appear to be always closed ingame (with the exception of her Eye and possibly Cat effects), though fanart and artwork from lol depict her eyes as being black or red. She has short white hair in a lopsided bed-head style. It's interesting to note that many of the hospital children and all of the Kaibutsus have white hair as well, which evidences possible speculation of the color being a physical manifestation of a disease.

Sabitsuki wears a dark, bluish purple top with a turtle neck collar and no sleeves. Additionally she has a white skirt and red shoes.

Her equipment screen (called "myself" in-game) has her whole equipment listed as:
 * Hair: Bed hair
 * Clothes: The usual
 * Skirt: My favorite one
 * Footwear: Leather shoes

Personality
In the fashion of Yume Nikki-styled games, the protagonist does not speak and much of her personal history is left to speculation. Many in the Western fan community depict her as one of the more volatile and aggressive of the Dreamers.

Throughout the game, there are motifs involving illness, hospitalization, and social exclusion, many suggesting that Sabitsuki is or was at some point in her life affected by an intense disease of some sort, possibly one that may have separated her from her peers at school. It can therefore be theorized that she is an excluded, introspective individual. Whether this is just a consequence of her status as a "disabled" person (having this disease) she has learned to deal with or Sabitsuki longs to reach out to other people is unknown—though it should be noted that the vast majority of the humanoid figures she sees in her dreams have parts of them decomposing or injured.

Sabitsuki seems to dwell on the unfortunate events of her past or negative thoughts that enter her mind: most of the dreamscape is comprised of dark and depressing elements, with the few exceptions of the Famicom world and the Rave Area. From the latter of these dimensions, wherein is found the Headphones effect, it can be speculated that she is or was an avid fan of electric music and technology itself, this interest being one of the few things she sees in a positive light.

Rust (銹)
By obtaining all of the effects in the game and depositing them in her PC, Sabitsuki transforms into a new version of herself, Rust. Rust cannot use any of the effects in the game, but can access three areas previously barred in order to obtain three empty boxes and obtain the last, and often considered true, ending. As of version 0.15, she can also get to an alternate version of the corrupted school. Rust's physical appearance is the same as Sabitsuki's, excepting the color palette, which is more pallid. In light of this and events of the third ending, many believe that Rust is Sabitsuki's more violent and diseased counterpart.

Having no access to the effects leaves Rust defenseless, though it should be noted that in lieu of the Kaibutsu there are now Red Demons in her dream world. These, upon contact, do not send the player to an inescapable area, rather, do physical damage to Rust. With each hit by the Red Demons, she becomes more decayed, until the point where she collapses and wakes up. It is theorized that the Red Demons represent a part of her disease.

Trivia

 * Sabitsuki's name continues the tradition of giving fangame characters a name ending in -tsuki. However, the kanji in Sabitsuki's name have a different meaning than the ones in Madotsuki's name. Sabitsuki means "covered in rust".
 * Sabitsuki looks like a witch (specifically Kiki from Kiki's Delivery Service) and rides a broom.