Kirschwasser is the nickname for the 99 Series Obversational Realian model. Kirschwassers have the appreance of 12 year-old girls with dark skin, milky white or silver hair and yellow eyes. Since the end of the Miltian Conflict, the 99 Series appear to have been retired in favor of the newer 100 Series Observational Realian models.
A large number of them were seen following U.R.T.V. #667 Albedo around during his younger days and later in life, but in Episode I he ultimately murdered a large majority of them once he became aware of MOMO's existence. The Kirschwassers who followed Albedo loved something they saw in him and stuck by him even when he was descending into madness. Many of the Kirschwassers envy MOMO on some level because they thought their "father" Joachim Mizrahi loved her more than all his other creations. On some level this was true, as MOMO was a Realian reconstruction of his lost beloved daughter Sakura Mizrahi. At the end of Episode II several angelic Kirschwassers supposedly descend from Heaven and carried Albedo away when he died. This may have been just another part of the massive illusionary state that Albedo had created within the space-time anomaly with the help of U-DO.
In the TV Asahi anime Xenosaga: The Animation, a slightly re-imagined retelling of the events of Episode I, a single Kirschwasser appeared as a fairly major recurring character. This character used to be Albedo's personal assistant Realian who escaped his custody and disguised herself as a new model 100 Series unit and snuck about the Galaxy Federation cruiser Woglinde. There she has a run-in with Shion Uzuki who strikes up a friendship with her; unfortunately she was recaptured by Albedo during the Gnosis attack on the vessel and was returned to her role as his servant. The story of the Kirschwasser in the anime was all about finding her own identity and her "heart" and trying to be good in spite of being surrounded and influenced by some rather evil people. The Kirschwasser ultimately sacrificed herself and went down with Proto Merkabah in the anime's final episode and saves Second Miltia from being destroyed by it. In the game this role is filled by KOS-MOS, though she survives while the Kirschwasser does not.
In Xenosaga I&II Albedo happens upon the Kirschwassers on Old Miltia when he is left behind after U-DO went out of control.