In Japanese, the name Shiki is used in both males and females. Although the word is pronounced the same, it is written differently in the Japanese language. For adaptation into English and other languages, distinction is made arguing SHIKI (in capital letters) for the male personality and Shiki to the female personality.
When Kokutou is out with SHIKI on their "date," the two cat dolls that they win from the UFO catcher is an allusion to Len and her white counterpart from the Tsukihime universe. As Len is mostly passive in nature, White Len represents the opposite with a very active and aggressive personality which is portrayed by the opposing look on their faces. Both Len and White Len can change from human into cat form where they wear a black and white bow around their necks, respectively.
Timeline: April 1995 - March 1996- June 1998.