『 』 is generally depicted by four game accounts, the main account being named 『 』, and the others named 『 SUB01』, 『 SUB02』, and 『 SUB03』, with Sora and Shiro controlling two accounts each. Note, that kanji for kūhaku (空白) is a compound made of kanji from names of both protagonists: Sora (空) and Shiro (白), which is probably how the name originated. ("空" can be read as "kū" and "白" can be read as "haku" when used)