When Syaoran, Kurogane, Fai and Mokona from Tsubasa kuronikuru (2005) visit Kobato's universe they are voiced by their actors from the series, Miyu Irino, Tetsu Inada, Daisuke Namikawa and Mika Kikuchi. Ioryougi even comments on Kurogane's voice as they are both played by Inada.
Based on a Japanese manga series by Clamp. It was first published in Shogakukan's seinen manga magazine Monthly Sunday Gene-X from December 2004 to August 2005, under the title Kobato (kari). It was later serialized in Kadokawa Shoten's Newtype magazine from October 2006 to July 2011.