Sebas-chan is a humanoid yo-kai with purple skin her head is blonde and tied in a bun that resembles a wisp flame, she wears a navy blue suit with yellow buttons. The lower half of her body is a ghost tail. Her pink lips and eye-mask resemble those of Whisper.
As Sebas-san, her face is wider and her expression more intimidating, she has horns on her head and a demonic smile with sharp teeth. Her eye-mask has long wings and her suit looks more military like, she's always holding a crimson colored whip.
Sebas-chan may be a corruption of "Sebastian" a name commonly used for butler characters in fiction, it may also be a reference to the actual Yo-kai Verygoodsir. The name uses the feminine honorific -chan.
- Her episode debut may be a reference to Siri.