A character from Stein's Gate and a Second year in Kasensou Private Preparatory Academy, and Mayuri's classmate. Born biologically male. He has the personality of a polite, well-groomed and justified kind of beautiful girl. He uses honorifics specifically with Rintarou. Doesn't push his opinions much upon others, but when he does he's quite bashful and blushes quite a bit. Because he's quite serious by nature, he simply believes what others say. Thanks to that, he thinks all the ridiculous stuff Rintarou talks about is that of reality. He's a very shy person, and often turns down Mayuri's requests to cosplay. Ruka Urushibara is a close friend and classmate of Mayuri Shiina and so-called protégé of Rintaro Okabe. While feminine in appearance and personality, Ruka is a male on most world lines. Mayuri often attempts to coerce him into cosplaying. He works at the Yanabayashi Shrine as a shrine maiden. He also has a secret crush on Rintaro Okabe "Delicate as an orchid, fair as a cherry blossom, the personification of feminine grace and also... a dude." - Rintaro Okabe describing Ruka

Luka Urushibara (漆原るか, Urushibara Ruka?) is a close friend and classmate of Mayuri Shiina and so-called protégé of Rintaro Okabe. While feminine in appearance and personality, Luka is a male on most world lines. Mayuri often attempts to coerce him into cosplaying. He works at the Yanabayashi Shrine as a shrine maiden.