Mayuri is a short girl with short black hair and lightly blue iris. Her hair forms fringes that sweep from either side. Mayuri's eyebrows are noticeably thick.
Mayuri's outfit is simple and comfortable, consisting of a light blue one-piece dress and a hat of the same color. She also wears leggings underneath her clothing.
When she attends to her work in MayQueen NyanNyan, she wears a blonde wig tied into a long ponytail.
Mayuri possesses an extremely childish and naïve attitude for her age. While this may have something to do with her inability to accept the death of her grandmother when she was young, Okabe states at one point that she's always been a little bit different, though he never goes into any detail beyond this. Mayuri has a great fondness for cute things like Upa cushions, and likes to give cute nicknames to familiar people, like Okarin for Okabe, being a portmanteau of his last and first names Okabe Rintaro, even referring to herself as Mayushii, being a portmanteau of Mayuri Shiina.
Mayuri is one of the less intelligent members of the lab, often misunderstanding or misphrasing information she overhears from Rintaro or Kurisu, though at certain times her responses can be quite helpful. She is also the one with the "clearest eyes" because she knew from the start that no good can come from Okabe's time traveling experiments (said by Okabe Rintaro while he was crying next to Kurisu about his inability to help Mayuri escape death on Friday the 13th). Mayuri also does not question Daru's perverted comments and mannerisms, or is not in any way offended by them.
Despite being socially inept, she is also responsible for Rintaro's well-being, usually tending to his needs most of the time. She's also very attentive to details, often noticing things about people that others would miss. She figured out Suzuha Amane is Itaru Hashida's daughter through the details on the Time Machine and from Daru's daily habits, suggesting a degree of skills in observation and problem-solving.
When Mayuri's grandmother died, she spent all her time in front of her grave; this constantly worried Rintaro. Mayuri was in that state for several days, until a very rainy day when she dropped her umbrella and started raising her hand to the sky (which according to Rintaro, was like she was being taken by her grandma). Rintaro rushed to hug Mayuri in the moment's notice to prevent her from being taken to the heavens by her grandma. Realizing what he did, he became flustered. Remembering a mad scientist show that they had watched together, where the mad scientist takes a hostage, he played it off as if it was all a part of his act. Concealing the real reason, Rintaro imitated the scientist from the show and declared that Mayuri is his hostage, so that nobody can take her from him. Crying profusely, Mayuri smiled a little and, with a frail tone, replied that it cannot be helped.
Mayuri's Ending Edit
Okabe must choose between saving Mayuri or Kurisu. Realizing that he harbors romantic feelings for Kurisu, Okabe and Kurisu decide to return to the Beta world line in which Kurisu's murder continues as planned, but Mayuri noticed that something strange was going on between Kurisu and Okabe so she decided to ask Okabe. After knowing about Okabe's journey to save her, about all people's happiness he sacrificed, and about Okabe's decisions, Mayuri cries and blame herself, running to see Kurisu. When Mayuri encountered her, Kurisu was packing her things to go back to America. She runs and hugs her, saying she doesn't want Kurisu to disappear, only to hear that this was Kurisu's decision from the beginning and that she wants Mayuri to be happy; saying that Okabe loves her, she parts. After hacking into SERN's database with the IBN computer, 1% divergence is achieved. Okabe vows to remember his memories of Kurisu, and spends his time with Mayuri as lovers. On a date with Mayuri, she says she had a very important friend that she doesn't remember who and that sometimes, she hears a voice, a voice that tells her to 'find happiness'. Mayuri holds Okabe's hand (Doing 'Stardust Handshake') and wondering if that important friend is the reason she is with Okabe right now, saying she wants to say thanks.
Before achieving 1% divergence, Mayuri dies in multiple ways during Rintaro's various attempts to save her, due to the events of the world lines in this same attractor field always converges into the event of her demise, though with different results each time:
- Shot in the head by Moeka Kiryu
- Hit by the Rounders' car
- Hit by a metro train
- Hit by a policeman's stray bullet
- Spontaneous cardiac arrest
- Gel-ified (VN, in the anime appears as a flashing image when Okabe described him repeating his time-leaping to save Mayuri)
- Shot by a Rounder whilst in a taxi with Okabe (Anime) / Stabbed by a Rounder whilst in a taxi with Okabe (Visual Novel)
- Gunned down by the Rounders
- "But isn't doing this bad? Mayushii doesn't want you to do bad things..." -Mayuri to Okabe.
- "We should work towards world peace. Like giving everyone an Upa cushion..." -Mayuri D-Mail wish.
- "Just look, we've made so many friends... There's Daru-kun, Chris-chan, Luka-chan, Suzu-san, Moeka-san, Feris-chan, Braun-san, Nae-chan and more! In the spring you seemed so lonely... But now you're fine. You don't need Mayushii to be your hostage anymore."
- "Finally... Mayushii was... useful... to Okarin." -Mayuri after protecting Okabe from being hit by a Rounder's car.
- "The whole time you and Chris-chan were hurting... While Mayushii was making costumes... like nothing was wrong... I feel so stupid! I didn't know anything! I need to see Chris-chan!" -Mayuri to Okabe after knowing what Okabe and Kurisu have been through.
- "Hum, I don't know who it was but Mayushii feels like she had a very important friend. And whenever I think about that important friend, my heart hurts, like hnng, you know? And sometimes, I hear a voice. That voice tells me to 'find happiness'. I wonder if that person is the reason of why Mayushii is with Okarin now... If I ever meet this person again, I want to tell them thanks." -Mayuri talking about Kurisu in her ending.
- Mayuri's voice was used as a user guide for the Phone Microwave. According to Rintaro, it made the Microwave sound silly.
- She was the first person to discover the Microwave's "irregular" abilities when she accidentally froze her chicken while trying to thaw it. She also gave the gelified bananas the name "gelnana".
- So far, the only ending of the visual novel in which Mayuri's death is definite is Luka's ending, as she survived in Faris's ending, Kurisu's ending (same thing applies to the True end), her own ending and Suzuha's ending (implied to have been saved through the combined efforts of Rintaro and Suzuha).
- Also, Mayuri dies of natural causes if Luka's ending was achieved. This is the one of two instances in the plot where the cause of Mayuri's death was not an accident/murder, the other being when she goes to ComiMa on the 16th after Luka's mail is reversed.
- Mayuri, like all other characters, has blurry memories of what happened to her in the other world lines, though unlike them she only thinks of the memories as "bad dreams".
- According to Okabe, his first kiss was with Mayuri in elementary school, though they were "just messing around".
- Lab Member 002. Second to the founder, already joined at the start of the main story. She joined because she saw that Okabe was lonely and she wanted to be with him (under the gimmick of being his hostage).
- Mayuri is so innocent and honest, Kurisu once thought that Mayuri was kidnapped by Okabe.