Yumemi Okazaki is an 18-year old college professor from Touhou Project, who appeared as both the final boss and a playable character in Phantasmagoria of Dimensional Dream.
Yumemi built the Hyperspace Probability Vessel, which she uses to pass through Gensokyo's Hakurei barrier in an effort to find sources of magic to bring back to her world for scientific research. During the events of Phantasmagoria of Dimensional Dream, her ship is mistaken for ancient ruins by the residents of Gensokyo, leading them to investigate. When she confronts the heroine, she attempts to kidnap her for scientific research, but is defeated. As compensation, she gives Reimu Hakurei an android named Ruukoto, and to Marisa Kirisame she gives an Intercontinental Ballistic Missile named Mimi-chan.
Yumemi is a extremely powerful character which utilizes a battery-powered laser pistol which can be thrown and retrieved akin to a boomerang and controlled on the way back to her and teleported to, energy grenades, missiles of varying sizes, and unusual magic with a cross motif. A vast majority of her attacks decrease the charge of the meter on the bottom of the screen, and when it is empty, these powerful attacks cannot be utilized until recharged, and if their gun is thrown, it can be left there, further preventing them from utilizing their devastating attacks until it is retrieved. Even with this disadvantage, among others, Yumemi has the ability to almost effortlessly annihilate most opponents in a hail of projectiles, as her attacks are frequently far too fast and extremely easily spammed.
Her AI is the typical, extremely high-level type expected of Touhou characters, although it is not on the same level as some more standard characters with brutally strong AI, and can be beaten by them.