There exist a few unsolved mysteries in Doki Doki Literature Club!. Currently, however, there's no confirmation that they hide anything; they might be meaningless.
Portrait of Markov
Portrait of Markov is the name of the book which Yuri reads with the player. It’s described as having an ominous eye symbol on the front cover and contents pertaining to a human experimentation camp. Monika remarks on this book in her 11th topic in Act 3. The significance of the word Markov is unknown, as it usually refers to Russian mathematician Andrey Markov, whose most well-known contribution to mathematics is the Markov chain.
The Markov chain is a mathematical process by which future outcomes can be chosen using only the probability of such an outcome given a certain state. It is usable within systems which exhibit the Markov property, related to the concept of memorylessness, in which only the current state of the system plays a part in determining the possible outcomes from that point, and the particular sequence of events leading to that state is immaterial. This may be a reference to the feature common to DDLC and most other visual novels where the same outcome can be obtained regardless of whether or not the game has been saved and reloaded. Notably, Monika exhibits some behavior which would indicate that she has a memory of events outside the game, such as her Save Me (Act 1) and Save Me (Act 2) poems, and her commenting on saves and reloads in her second topic.
In Act 2, there’s a chance of Natsuki with black pixels covering her eyes, a realistic mouth over her mouth, and saying “mibulls sailcloth blindsight lifeline anan rectipetality faultlessly offered scleromalacia neighed catholicate”. These words, though apparently random, might have meaning, though this has yet to be discovered or even confirmed.
The final poem which Yuri shows to the player in Act 2 (mdpnfbo,jrfp) appears to be groups of meaningless words separated by two commas each followed by a coherent paragraph. Though no successful translations of the first section have been made, some suspect that it may be a cipher of some kind.
A possible explanation for the first section of mysterious poem is that the poem is intentionally made to resemble Markovian Parallax Denigrate, an unsolved internet enigma from the early days of the internet in which mysterious forum posts entitled "Markovian Parallax Denigrate" containing similar random gibberish words with very little coherence to each other were being flooded through many of the early internet forums. Although there has been no firm evidence supporting this theory so far, the many references that Yuri made to the name Markov made this explanation a likely one.
Possible information useful for deciphering the text might include (but is not limited to) the location of each group of two commas, the number of letters in each word, or the first characters of each word. The words are generally grouped together in a repeating pattern of 1-2-3-4-5-4-3-2 by the commas, but there are several exceptions to this.
Contained in the
audio.rpa archive of DDLC is a file called
eyes.ogg, which can play during Act 2. It appears to be a sped up deep voice saying "give me up," "get me out," or a similar phrase, followed by an unclear background noise.
In the background art for Sayori's room, one corner of her calendar has been torn off, and November has been scribbled out. In Japan, club fairs such as the one led up to by the game are often held around this time, but any significance of these dates is purely speculative.