Yumemi is the 18 year old professor of comparitive physics at an unnamed university, which is in a world far from Gensokyo. She has red eyes and dark red hair, with a matching cape, vest and skirt. She also has a white shirt and a bright red bow-tie. In Yumemi's world, all of the forces, such as gravity, electromagnetism and atom power have been resolved under a gran unification theory, which has been proven to explain all the known forces in this world. However, Yumemi believes that there is one force which doesn't fit under this theory: magic. When she presents an expanded theory that included magic in it to the academic society, she becomes a laughingstock.
She is one of the main causes of the events in Touhou 03 - The Phantasmagoria of Dim
(alongside Chiyuri), as the "ruins" that attracts the attention of everyone present in the game is actually her ship, which she calls a "Probability Space Hypervessel". She travels to Gensokyo so she can do some research and data gathering on magic, allowing her to solidify the expanded theory and get back at the academy. After the survivor of the challenge created by Chiyuri defeats Chiyuri, Yumemi makes an agreement with her: if she wins, she gets to take the survivor home so she can do research on her, and if she loses, she will reward the survivor handsomely. In the end, she loses, and goes home empty handed.
- "Yumemi" means "beautiful dream", while "Okazaki" is a common Japanese surname which means "mountain"