Monster Princess” Do-S (怪人姫弩S, Kaijin Hime Do S; Viz: Monster Princess Super S), often simply referred to as Do-S (弩S, Do S; Viz: Super S), is a Demon-level Mysterious Being and a member of the Monster Association.

Do-S resembles a human female with long, blonde hair with a black flower on the left side of her head. She has a curvy body type, pink eyes with black sclera and a pink, heart-shaped symbol on her forehead, as well as many piercings on both ears. She dresses in a very revealing BDSM outfit which is made of tight straps and held by metal rings that show off her curves. The straps connect at two points on her torso, both with rings at their centers, the first above her chest and the second on her belly, with the ring encircling her navel. Her right hand has two spiked leather rings and a leather vambrace, while her left hand has a very long leather glove with holes in it. Her attire is adorned with high-heeled boots and rips armed warmers. In addition, she also dons a mask with an “S” symbol over the filters as well as a spiked choker. Her unmasked face has a wide, cracky mouth, sharp shark-like teeth, and a long, flexible, slimy tongue.