Len

Len (レン) is the main heroine in the main story of the fandisc, Kagetsu Tohya. She also appears in Melty Blood ReACT. At the end of Kagetsu Tohya, she formed a contract with Shiki and is now his familiar. She is voiced in Melty Blood ReACT by Mizuhashi Kaori.

Backstory
Len is a Succubus Demon Familiar with the ability to manipulate dreams, created from infusing the soul of a deceased human girl into the body of a cat. As such, she is capable of shifting between the forms of a black cat and a prepubescent human girl. She once served a Magus several centuries ago, after whose death she was taken under the care of Arcueid Brunestud. Although she was under Arcueid's charge, because Arcueid is not human, they were unable to create a contract, therefore Len is not considered Arcueid's familiar.

In Tsukihime
In Tsukihime, Len appears indirectly in the "Near-Side route". She gives Shiki a dream of a sexual encounter (which can include any of the heroines: Arcueid, Ciel, Akiha, Kohaku, or Hisui). She is never mentioned by name. Since she is sent by Aruceid, and Aruceid wishes to know who came to Shiki, an interesting scene occurs if Aruceid is picked.

Kagetsu Tohya
In Kagetsu Tohya, Len is the main heroine. When the main character, Tohno Shiki, falls into a coma after an accident, she takes it upon herself to keep him alive by putting him through a recurring dream sequence, repeating the same day over and over, his memory wiped clean for each day. Things start to get chaotic, however, as Shiki's split psyche, as well as her dangerously, even fatally, low reserves of prana, causes things to fall apart. Len puts her all into keeping things in order, while Shiki is slowly starting to gain a realization of his situation. After fighting his other self ("Nanaya Shiki") and confronting his image of death (Kishima Kouma) he meets Len in the courtyard of the Tohno Mansion and is able to form a contract with her.

Romanization
Many fans use the romanization 'Ren' instead of 'Len',　as that is the standard reading of the name's katakana. The 'Ren' version has more history, and stems from the use of that spelling in Kagetsu Tohya's script and file names; however, it was not used in text visible to the player in that game. All versions of Melty Blood, which prominently feature romaji versions of all character names, consistently spell her name as 'Len'. It is unknown which is the 'real' romanization, as both could be correct (katakana is usually for foreign words and names, which do not always adhere to the rules of the Japanese language). The translation groups Revolve uses 'Len' in their Melty Blood translations, and the Kagetsu Tohya translation project followed their example. However, many doujin scanlations, in particular older ones, use 'Ren'.