Luka Urushibara 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.

Honestly this role is  androgynous so I don't mind if a male or female or whoever auditions. I just want the shy/naive portrayal! In fact in some time lines they are female so just go for it!