 During early planning stages, director Gorō Taniguchi contacted the noted manga artist group Clamp, being the first time Clamp had ever been requested to design the characters of an anime series.Clamp signed onto the project early during these development stages and provided numerous ideas, which helped develop the series' setting and characters.Clamp's finalized original character design art, illustrated by its lead artist Mokona, was subsequently converted into animation character designs for the series by Sunrise's character designer Takahiro Kimura, who had previously spent "every day" analyzing Clamp's art and style from their artbooks and manga series.