Petal's character is meant to be from the oldest time period in the story, thus her design is heavily based on Ancient Greek art and fashion. She wears a traditional Greek "traveling costume," as she travels throughout the story. She wears a chlamys, a chiton tied with a belt, and greek sandals. Even her side profile is inspired by the side profiles on ancient greek pottery.
The Gardener's from the second oldest time period, Edo Period Japan, and specifically the early 1600s. Her face is modeled after art from the era. Her face is modeled after the Japanese concept of "kitsune-gao" or "fox-faced." People with this face shape were said to be attractive but also foxes in human form. Foxes are generally thought of as shifty and untrustworthy, which is foreshadowing that she may not be what she seems.
On the last page of the first chapter, the Gardener transforms into a monstrous form. Her design is based on Japanese oni masks, which are a type of Japanese demon. One of the most challenging parts of this design was making her look scary and monstrous, while still keeping some of her original design.