Also called Mayushii, is Rintarō Okabe's childhood friend and companion. She works part-time at a maid cafe called May Queen Nyan-nyan as a costume maid and occasionally makes cosplay outfits. She is usually the one who financially supports Rintarou's "research" when food is needed.
She possesses an extremely childish and naïve attitude for her age. This may have something to do with her inability to accept the death of her grandmother when she was young. Mayuri likes to give cute nicknames to familiar people, like Rintarou (Okarin), and refers to herself as Mayushii. She often misunderstands or misphrases information she overhears from Rintarou or Kurisu, though at certain times her responses can be quite helpful. Also, Mayuri does not question Daru's perverted comments and mannerisms, or is not in any way offended by them (though this is likely because she does not interpret them as such). (steins-gate.wikia.com)