Madotsuki (窓付き) (pronounced /mɑˈdɒtsuː.kiː/) is the protagonist of Yume Nikki. She is one of the three characters in Yume Nikki with an official name, since characters require a name for the menu screen in RPG Maker games (the other two being Monoko and Monoe, specified in the filenames of their image files).
As with virtually everything else in the game, Madotsuki's identity and life are a mystery. Only what can be seen in-game can be considered canon, although there are many varying interpretations of her.
Fans speculate that she is young - anywhere from a young child to an early teen - although arguments can be made for any age.
Madotsuki is a playable character in the fighting game M.U.G.E.N, and in fan games and artwork she is commonly portrayed wielding her iconic kitchen knife.
Name
The word "Madotsuki" means "window" (as in a box or envelope) or "aperture" (see its dictionary entry here ). The name appears in the menu as the name of the player-character, and (in the Japanese language version) is the only place where kanji appears in the game. All other text in the game—the game menus, instructions, the "menu has changed" notice, Nasu, and even the title screen of the game—is written using the hiragana alphabet.
'Madotsuki' is not a word used as a name in Japan - in fact, it may not even be her true name at all. It could be thought of as being a metaphor; more a description of the character as the 'player's window into the dream world' rather than a literal name. It could also be a way to preserve the game's theme of loneliness by giving the character a functional, dehumanizing name, rather than a personal name.
It is similar to the colloquial Japanese term for 'windower', a person who spends a long time looking out the window; that is, a daydreamer.
It has commonly been noted that when you reverse her romaji name (Madotuki in Kunrei-shiki romanization), it becomes Ikutodam: 行くと駄目 or 行くとダメ ("iku to dame"), a commonly used phrase that means "it is useless to go/leave."
Real life
Madotsuki doesn't have much to do in her room. Her television set doesn't receive any channels, so she can only use it to play a single game, NASU. She can go outside on the balcony, but the balcony itself must be rather high as her view always seems to be blocked by fog.
Madotsuki's dreams
Elements in Madotsuki's dream world seem to hint at her mental or emotional state. Some effects seem to show her unhappiness. The knife, in particular, appears to hint at her misery. However, the player ultimately controls Madotsuki -- it is unknown whether she would use the knife on her own.
Since many dreams are disturbing when shared, Madotsuki may just be a typical lucid dreamer trying to find a release from her sadness by exploiting her dreams for fun and self-discovery.
Fan speculation
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Hikikomori
The most widely accepted theory among fans is the that Madotsuki is a hikikomori, evidenced by by her refusal to leave her room; if a player attempts to leave, she merely shakes her head. The speculation for why this is is disputed.
Mental illness
It is possible that Madotsuki is depressed (For whatever reason, perhaps chemically or acquired), and that her dreams are caused by her medication. (Most anti-depressants cause vivid dreams due to higher serotonin and instances of REM rebound) Depression would explain her images of despair, hopelessness, and end-game tendencies. And while antidepressants are the most infamous, other psychoactive drugs have a tendency of causing strange dreams as well, that she may be taking. Alternately, perhaps she has had such an illness since she was born.
Confinement
Madotsuki might have been kidnapped, and have been locked in her room for a long time. It has been a theory that she thus goes to the dream world in order to escape from present reality. Perhaps both her parents (or foster parents) might have been the ones to lock her in for some reason.
Psychic abilities
Due to how varied the dream-world is, it might be possible that she has psychic abilities to wander into other people's dreams. The madness of the dream-world might have driven her insane.
Dream within a dream
Perhaps the world in the game thought to be the real world is actually also a dream, and that she is seeing a dream within a dream. Combined with the "traffic accident theory," she may actually be in a vegetative state.
Gender
Due to the recurring images of orifices, blood, and a road with womb-like creatures, and the fact that Madotsuki uses both the men's and women's restrooms in her dreams without hesitation, Madotsuki may question their assigned gender. This can be taken in either direction; Madotsuki could be born assigned as male or born assigned as female. The former theory is supported by KyuuKyuu-kun, who looks like a phallus followed by a disturbing face in the shape of a penis head, complete with a possible urethra, while the latter possibility is supported by the fact that a trans person (transman, in this case) could not or would not come out as male due to safety issues. All normal humans (styled just like Madotsuki) in her dreams are female, all of whom are difficult to interact with. This would show her fear of fitting in with other females due to the fact she is not a cisgender female. The fear of rape induced pregnancy would also only be an issue if one was born assigned as female, so Madotsuki could be a trans male, and KyuuKyuu-kun and other penis shaped objects may be another image of the assault theory.
Foreign
Some fans believe that Madotsuki isn't Japanese, but American, English, or other nationality. (This theory, however, is limited to people outside Japan - not many Japanese people have ever referred to Madotsuki as a foreigner, or even mentioned the words 外人, 外国人, or 異国人 ("gaijin," "gaikokujin," and "ikokujin") in reference to her, or anything else in Yume Nikki for that matter.) The creator of the game is Japanese, and Madotsuki's apartment looks Japanese, yet her furniture is Western looking. An example is that the bed she sleeps in is not a typical Japanese bed. All these facts lead many fans to believe that one of the reasons to Madotsuki's shut-in behavior is that she's living in Japan, but is a foreigner. She doesn't know Japanese, and feels isolated from the rest of the world because of this. This theory has been made due to the fact that there's no dialogue in the game, only numbers and sounds and the one 「あ」. (Except for when you try to make her leave her room when she's awake or try to use an item's power when it's incapable of doing so; she will occasionally say "no" in Japanese when shaking her head "no". This also happens when you try something she can't do, like trying pinching yourself with a effect with no hands, she will say "Can't" or "Impossible" in Japanese; too fast, but cute.) Speech and letters is what defines a language, and Madotsuki tries to distance herself from that.
Trauma
Traffic accident
It is thought that Madotsuki was involved in a traffic accident in her past -- the same accident that Monoko is speculated to have been in. The bloated abdomens found in Madotsuki's dreams may be images of her decapitated and pregnant mother. The severed heads in the monochrome world could be people who died in the accident and may perhaps include Madotsuki's mother and father. Monoe may be a deceased sibling. Madotsuki's ghost could refer to injuries sustained by Madotsuki during the accident; alternatively, its placement in Hell could be a reference to survivor guilt.
The Severed Head effect may be linked to the decapitated mother and father in the front of the vehicle. The Stoplight effect could be linked to the accident happening at a stoplight.
Alternatively, there is also a theory that Madotsuki herself was the one involved in the traffic accident, and that Madotsuki is actually already dead from the beginning.
Assault
It is possible that Madotsuki was raped prior to the events of the game.
Her self-imposed exile could be an example of shame and self-blame over the incident; the presence of her "ghost" in Hell could support this. The existence of the phallic KyuuKyuu-kun monster and the possibly-phallic FACE cutscene (both in close proximity to each other) could represent a fear of re-victimization. Hands and eyes are also common throughout the dream world, possibly referring to both rape and shame.
Various monsters take the form of deformed pregnant women with slashed throats or severed heads, implying a fear of rape-induced pregnancy.
Poniko could be a dream-based replica of Madotsuki prior to the incident in her past. Alternatively, Poniko could be a metaphor for confidence and happiness that were replaced by helplessness (Uboa) during a random incident that happened in the dark. Or Poniko was really a person who harassed Madotsuki or sold her to a stranger represented by Uboa.
Paracas Similarity
An image depicting what probably is a “sacrificial maid” has been found on a very ancient poncho:
This one basically reafirms all the other evidence related to what was considered “aztec” (such as the aztec rave monkey” and the floating magicians at the nexus) to be really influenced by this culture.
And who knows? Maybe Kikiyama himself looked at this image to create Madotsuki.