Some poser who claims to have created the Neptunia series. She is currently held in Cell 13 of the Nanba prison, which is located in a remote island somewhere near Japan.
She wears glasses.
Mizuno showed up to the Compile Heart offices sometime in early 2010, as the development of Hyperdimension Neptunia was coming to a close. She claimed to be the original creator of the Neptunia series, and that she had brainstormed many of the concepts that made it into the final game with Tsunako, back in 2000 when development began. She furthered her claims by stating that she was a prisonner of war in Vietnam for the past 10 years, as an explanation for her absence during the entire development of the game, a claim which seemed to be backed by her ragged appearance. Moo Niitani, CEO of Compile Heart who had joined the development long after it had began, asked Tsunako for affirmation of Mizuno's claims. However, Tsunako denied everything Mizuno had said, and instead stated that Mizuno had been stalking her since 2000, and the reason why she hadn't been seen in 10 years is because she had been arrested and spent those 10 years in prison. The two then got into a heated debate which continued for 2 days and 2 nights, at which point Mr. Niitani called the police to have Mizuno removed from the premises. This resulted in a 500km restraining order being placed on Mizuno.
The very next day Mizuno violated the restraining order by entering Compile Heart offices again to demand being let onto the Neptunia dev team. Her demanding quickly turned to pleading, and eventually even offered to work for free, but Mr. Niitani refused. When Tsunako saw Mizuno in the office yet again, she immediately called the cops, and Mizuno was sent straight back to jail. She did not pass GO or collect $200 on her way out.