Mayu Sumimori


 * This article contains major plot spoilers from the manga that have not been revealed in the anime. Proceed at your own risk.

Mayu Sumimori (住森 麻夕) was in charge of the accounting and intelligence gathering for the CCC, in which she went under the code name Eleven (イレブン). However, after she was deemed to be no longer useful, she was left to be killed by the organization, but she was saved by the F Squad and restarted her life outside the CCC.

She comes from a wealthy family who had connections to the CCC. She has an inferiority complex due to having beautiful parents and sisters, and she doesn't feel as pretty as her name sounds.

History
Mayu Sumimori comes from a wealthy family, she is the third child born to Katsuki and Saki Sumimori. Her older sisters are Mana and Kaori, and her younger sister is Mio. Ever since she was a child, her father always fussed over her sisters but never her. Mayu says it was because her whole family was beautiful except her. While her father was very protective of her other daughters while Mayu didn't get any attention, she decided to get a job to save up money since she had only holed herself up in her house either way. Mayu's father had connections to Kirio Kikuhara, so Mayu was able to get a job at the CCC. Although Mayu's family were told that Mayu would only do clerical work at a trading company, she was, in reality, working for an organization aiming to exterminate devils from the world. Mayu hadn't given the job a serious thought, but Kikuhara said that he was looking forward to working with her. Somewhere between this time, Mayu appeared to fall in love with him. She then became the CCC's accountant.

Appearance
Mayu is a young woman with a light and fair complexion. She has dyed, straight blue hair, which is nape-length with middle-parted bangs. She has light-blue colored eyes and wears makeup. After some events, Mayu gains weight and develops a fuller figure and plumper lips. She occasionally has her hair tied into a ponytail with her bangs held back by two hairclips at each side, in which her hair has grown longer. She has inherited most of her father's appearance, and is noted to have looked exactly like him before he had plastic surgery. Mayu also doesn't feel beautiful and is planning to get plastic surgery as well.

Personality
Although Mayu is the account of the CCC, she is clumsy and not good at detailed work as she often makes mistakes. When she was in the CCC, Mayu followed Kikuhara's (Zero Two) ideologies about exterminating devils from society and strongly supported the Plan B (The Ikebukuro Incident). She was obsessed with Kikuhara and deemed everything he did was right. So when people disobeyed him, Mayu was seen to be highly cruel and violent, furiously beating up Zero Nine when he was against Plan B. She didn't care if the other CCC members died, only if they could be useful to Kikuhara. Mayu is therefore noted to be very arrogant and pretentious. She is very blunt and is not afraid to say what she thinks, especially when it revolves around people's poor working skills.

After deserting from the CCC however, Mayu became truer to herself. She is noted to be like her father in terms of personality, cowardly and fragile. She cries easily when she gets called out on her mistakes and is not above cursing at people who look down at her, such as Mana. Because of her father's comment on how ugly she is, and because her whole family is beautiful, Mayu developed an inferiority complex and is determined to get plastic surgery to become the most beautiful in the Sumimori family. She works very hard to earn money so she can pay for it herself. This shows that Mayu is hardworking in her own way.

Mayu has always been very impulsive and driven by her feelings, always wearing her emotions on the sleeve. She tends to overthink and overreact in different situations. She is very flustered and giddy in her love's, Makimura's, presence. Mayu is sometimes dishonest with her feelings and at other times she is quite direct and doesn't beat around the bush with her words. When she falls in love with someone, she takes their words into consideration more than she takes from someones else. When she fell in love with Makimura, it was genuine, and not an obsessive, fake love like her attraction towards Kikuhara.

Mayu deeply cares for the people she holds close, and appears to be kind and energetic. But she is not very smart and has difficulty learning hard, sometimes even basic things. However, Mayu is good at housework and is confident that she will be able to handle that, though she claims she might become bored with it sooner or later.

Kirio Kikuhara
Mayu claimed to be in love with Kikuara. She was highly obsessive with him, and did everything he asked. She would often act in her own way and on a whim if it would please Kikuhara. Though she felt like they were connected and that they trusted each other, all of it was one-sided. It is unknown if Mayu's love for Kikuhara was genuine, as she seemingly only loved him because he was "perfect", so when he slightly messed up the Plan B, Mayu was angry that he wasn't "perfect" anymore and her feelings towards him faltered.

Takeshi Makimura
Makimura and Mayu were in the CCC together, and they were never above scolding and criticizing each other wrongdoings. Mayu didn't particularly like Makimura and saw him as quite scary and unapproachable. After he helped her recover from an injury though, Mayu started to develop some feelings for him. However, she was in denial of her own feelings and ensured that she only liked Kikuhara. But when they began chatting more, Mayu saw a different side of Makimura and truly fell in love with him. He was kind to her and ensured that she was naturally pretty when Mayu spoke out of her desire to get plastic surgery. However, their relationship took a turn when Makimura was ordered to kill Mayu by Kikuhara. Although he didn't want to kill her and left her in a near-death state instead, Mayu was disappointed and hurt that her feelings didn't get through and that she had actually hoped for a relationship with Makimura. But when Makimura later apologized to Mayu and told her to ignore the people who commented on her looks through a broadcast, it deeply touched her.

In the aftermaths of the CCC raid, Mayu saw when Makimura in a near-death state himself, so she took him to a safe place and sought medical attention from her family. During the time Makimura stayed at her home, Mayu took care of and helped him, and she also stayed by his side the whole time he rehabilitated from his injuries. Makimura even rejected Mayu's "beautiful" older sister's (as Mayu claims) advances, noting that Mayu is the one he wants to be with. This made then develop an even stronger bond and Mayu fell more in love with him, which she confessed twice. She desires to stay by his side and support him. While Makimura clearly is deeply in love with Mayu, he isn't sure of his feelings and has yet to give Mayu. Currently, they have a very close and deep bond of trust and they are very comfortable with each other. Makimura is the only person Mayu has genuinely liked.

Trivia

 * Mayu has a very rough way of speech, which is traces of her delinquency in her teens.