Katsumi Nakase, widely recognized by her cosplay alias Fubuki, is a second-year high school student within Mayuri Shiina's circle of friends. She possesses short, light brown hair styled in a fringed bob and light brown eyes. Her distinctive attire features a bright-yellow jacket with black zigzag patterns on the sleeves, layered over a beige hoodie and pink shirt. Fubuki feels self-conscious about her boyish appearance, which contrasts with her affinity for cute outfits and accessories. Athletic yet enamored with feminine aesthetics, Fubuki displays a brash, unfiltered personality. She speaks unreservedly, often engaging in playful flirtation with Mayuri and others—behavior her friends occasionally jokingly term "sexual harassment." Her impulsiveness renders her poor at lying or guarding secrets. Like Mayuri, she is an otaku who enjoys anime, video games, and cosplay, favoring male character portrayals due to her appearance. Her sociable nature allows her to forge friendships effortlessly, as observed during hospital stays. Fubuki met Mayuri at a cosplay event where Mayuri crafted costumes for her, including a notable portrayal of Seira Orgel from *Blood Tune* that Mayuri deemed "sexy." Outside cosplay, she maintains school friendships but remains the sole member of her group without a boyfriend. In the original *Steins;Gate*, she briefly appears in select Alpha World Lines, meeting Mayuri at a Starbucks on August 13 for costume adjustments. Her role expands in *Steins;Gate 0*'s "Closed Epigraph" chapter, where she becomes a viewpoint character. She contracts an encephalitis-like illness linked to developing Reading Steiner, enduring vivid flashbacks of Mayuri's repeated deaths across Alpha World Lines and visions of World War III in Beta World Lines. During a Christmas party, she and Rintaro Okabe collapse simultaneously from a world-line shift, leading to interrogation by a man named Shimoyama. Fubuki inadvertently discloses knowledge of an alternate world line where the Soviet Union persists. Hospitalized afterward, she receives visits from Okabe, Mayuri, and their friends. Okabe confides in her about Reading Steiner and world lines—information later acquired by Professor Alexis Leskinen, strongly implying Fubuki was brainwashed into revealing it. In a World War III-affected world line, she suffers injuries during Tokyo's Great Bombing before reuniting with Okabe. Her closest bonds are with Mayuri, whom she affectionately calls "Mayushii," and Kaede Kurushima, an older sister figure. She also befriends Yuki Amane and interacts with Faris Nyannyan and Luka Urushibara through Mayuri. Fubuki harbors distinct dislike for Itaru Hashida due to his perverse remarks, rejecting comparisons to him. Her dynamic with Okabe remains distant; he visits her hospital primarily to avoid "the wrong idea," though she voices concern for his well-being and subtly encourages a relationship between him and Mayuri.