Medusa (Japanese: メドゥーサ Medūsa) is a Onryo who is the main antagonist of M06, responsible for one of the Seven Academy Mysteries. She has two additional forms, who are named Togurosu (Japanese: トグロス Togurosu) and Onrei no Tamago (Japanese: 怨霊のタマゴ Onrei no Tamago).
- M06: Major Antagonist
- Yo-kai Watch: Wibble Wobble: Playable Yo-kai
- Yo-kai Watch Jam - Yo-kai Academy Y: Waiwai Gakuen Seikatsu: Boss Yo-kai
Medusa appears to be a very slender Onryo. Red snakes form her hair (like her Greek namesake) and four make up her arms. The snakes that form her hair make a heart-like shape. She has a small green head, half of which is hidden by snakes, and a skeletal body. Her shoulders have three spikes on them. There are two small arms extending from her rib-cage. She lacks a pelvic bone and is levitating over her lower body, which consists of her legs and a wing-like dress.
Her secondary form, Togorosu takes the shape of a dark-gray and green-spotted piece of poop (yet still retains a rolled-up cobra body if look closely to her 3D Model in Yo-kai Watch Jam - Yo-kai Academy Y: Waiwai Gakuen Seikatsu) , with snakes lurking out of it and and on the top. She also has red eyes with purple eyelids, yellow pupils and eyelashes and big lips with red lipstick on it.
In her third and final form called Tamago, which is shaped like a egg with legs and scythe-like hands. She has a light-grey body with red stripes and black and white eyes on each, with a mouth that is always open along with a white tongue inside.
Medusa has several reptile-like minions that work for her, which are the students that were turned into Uwabami. She also has the abilities to turn into two other forms, Togurosu and Tamago.
She is based on the Gorgon of the same name, who was in love with Poseidon. Medusa was once a beautiful lady but became her hideous form after she and Poseidon made love in the virgin goddess Athena's temple, forcing the goddess to change her into a gorgon, and help Perseus slay her.
- Medusa is tied with The Ghoulfather of having the most distinct boss forms.
- Medusa has the most distinct forms out of all Boss Yo-kai that are not final bosses.