The D-Cellophane (Dセロファン, di serofan?) is an small cellophane made out from a Grathnode Crystal base, which contains the DNA seeds for a Reyvateil, and it's an enhanced version of the HD-Cellophane. Due to being made out from Grathnode, it has similar properties to it, and as such, it can also be Installed and Uninstalled.
The D-Cellophane is an essential part of one of the Reyvateil Origins and of all the Pureblooded β-types, due not only to containing part of the data that links the Reyvateil's body with her Cosmosphere, but also because of it being a checksum for the growth of the Reyvateil.
Whenever it validates how the Reyvateil is growing, the Spectrum Gene recorded in the D-Cellophane is compared against the Real Spectrum the Reyvateil has at the time, and then, the D-Cellophane judges if the growth is within her tolerance level. If there are any anomalies, the LEM will send a signal to correct them, and afterwards, it proceeds to make the Reyvateil grow by allowing the sending of waves from the Triangular Nuclear Loop to her body.
The D-Cellophane is not needed for a Reyvateil to reach maturity, but if it's extracted before she reaches that stage, the LEM will invoke at once the instruction to completely halt her physical growth. Also, unlike the HD-Cellophane, which serves as a ROM drive, the D-Cellophane serves as a rewritable storage media, which allows the Reyvateil to grow, mature, and learn. Likewise, it also allows large changes to her personality and behavior.
The information recorded in the D-Cellophane it's also used for transcribing genetic data because of its nature, one of its principal applications being cloning. It was in this way that all of the Reyvateils in the Lune Lineage were made, and likewise, most of the Reyvateils living in Clustania. It's because of this that it's also used for creating the Hymn Code identifier that all of the Pureblood Reyvateils have. However, the D-Cellophane is unable to manage beyond an small amount of genetic data, reason why factors like physical appearance aren't transmitted through it. It only affects the most fundamental part of the Reyvateils, which is what we know as the Spiritual Standard Frequency: the base frequency that determines the personality and mentality of each Reyvateil, which is unique to each of them.
Also, two Pureblood Reyvateils should never share a D-Cellophane under any circumstances, because this would create a new problem: they would have the same Hymn Code, but also, their Cosmospheres would be registered under the same address within the SH Server, which will cause a great rivalry between both of them, as well as also causing incessant problems of confusion between their mental states.
Other usage the D-Cellophane has is being used for Preinstalling Hymmnos Extract songs, which is normally made by inserting the feelings of the song into the D-Cellophane in a similar way to the creation of an Hymn Crystal, although this process is generally reserved only for Reyvateils that will have an specialized function, and important reasons for being created. This also increases the level of security for the Hymmnos Extract because the only way to leave the Reyvateil unable to sing it would be Uninstalling the D-Cellophane from her, something that is normally hard to achieve due to said Reyvateils being under very heavy protection, but still not unheard of.
The very first Reyvateil to use a D-Cellophane was the Reyvateil Origin Frelia, who served pretty much as a prototype for the development of the Pureblooded β-type Reyvateils.