Katsumi Nakase

Katsumi Nakase (中瀬 克実, Nakase Katsumi), who goes by the alias Fubuki, is a cosplayer and friend of Mayuri Shiina and Kaede Kurushima. Due to her boyish appearance, she is better known for cosplaying male characters than female ones. She is mentioned in Steins;Gate and is a side character in Steins;Gate 0.

Plot
(SPOILER ALERT)

Katsumi is one of several who contracts the new encephalitis disease, the symptoms of which include strengthened Reading Steiner. As a result of this, she begins to have flashbacks to Mayuri's many deaths in the Alpha Attractor Field.

Vega and Altair Route
During the Future Gadget Laboratory's Christmas Party, she and Rintaro Okabe both collapse as the world line changes to one where World War III has begun earlier than Suzuha Amane foretold and the Soviet Union still exists. A man by the name Shimoyama interrogates both her and Rintaro, tricking both of them into revealing that they know of an alternate world line where the USSR hadn't fallen.

After the worldline changes mysteriously once again, Rintaro discovers that Katsumi is still hospitalized after collapsing from Reading Steiner's effect on her body, so he, Mayuri, and her friends go to visit her. While there, Rintaro confides in Katsumi the secrets of Reading Steiner and worldlines, which Professor Alexis Leskinen later learns from her. It's heavily implied that Professor Leskinen brainwashed Katsumi to obtain this information.