Mary Sera

Mary Sera (メアリー 世良 Mearī Sera?), also known by her marriage name as Mary Akai (赤井 メアリー Akai Mearī?) who appears to be a girl with light hair was shown hiding in Masumi Sera's room. The child's eyes have a remarkable resemblance to those of Shuichi Akai and Masumi Sera. Despite her appearance, she is actually a middle-aged woman; she is the mother of Shuichi Akai, Shukichi Haneda, and Masumi Sera. She is a member of the British Secret Intelligence Service, often known as MI6.

Appearance
The child appears to be a female of middle school age (12-15) with light colored, curly, neck length hair. The child has eyes similar to those of Masumi Sera and Shuichi Akai. In her appearance in File 877, she was shown wearing a high-neck pleated top, hoodie jacket, and hat.

Appellations
Friends and Relatives=
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Plot overview
===The Red Woman Murder Case (Manga: 875, Anime: 756)===

Masumi asks Conan to find her cellphone by calling it with his. When he does he notices the call background screen is a child with eye bags similar to those of Shuichi Akai and Masumi Sera. He remarks that the girl looks similar to Masumi. Earlier in the case she only mentioned having two brothers; a mother; and a father, so Conan suspects Masumi was intentionally trying to show him the child for some reason. ===Romance Novelist Murder Case (Manga: 876-878, Anime: 759-760) ===

When Ran, Sonoko, and Conan visit Masumi's apartment, the child is shown opening Masumi's door as Conan, Masumi, Sonoko, and Ran rush to investigate a crime. It is implied she was hiding in Masumi's bedroom while the other three were in the dining area because Masumi asks Conan not to enter her bedroom. The child later goes downstairs to the scene of the crime where she is seen by Conan. At some point off screen Conan leaves behind a bug in Masumi's room. After the case is solved, the child is shown examining Conan's bug along with Masumi. The child comments on the quality of the performance of the bug itself and that she has never seen one like it. She says that it is still early to trust Conan, and asks Masumi to introduce her as "the little sister from outside the domain (領域外の妹 ryōiki-gai no imōto)", should Conan question her in the future.

Shogi Tournament (Manga: 899-902, Anime: 785-786)
The child is interested in Shukichi's Shogi match. When Masumi returns to the hotel room in the middle of the case while the child is napping, she turns on the tv and sees the Shogi match. Later after the case is solved, Masumi enters the room for a second time to see the child turning off the tv. Presumably she saw the end of the match and was happy at Shukichi's victory, as was Okiya Subaru, whose identity was revealed in the case before this one, to be Shuichi.

===Poolside Case (Manga: 903-905, Anime: 787-788) ===

The child is waiting for Conan to visit her and Masumi in their hotel room. She expresses her still-lingering concern of trusting Conan, even though she thinks he is bright enough. The child does comment that if anything were to go wrong they would have to move hotels again. Her talk with him alone is put on hold, however, because Ran and Sonoko have invited themselves in accompanying Conan in order to enjoy the hotel's pool. As Conan, Ran, and Sonoko head back home after the case is solved, Ran turns around and sees Masumi talking to her. Ran gets the feeling that she has seen that child before.

A Killer in Ramen Ogura (Manga: 928-930, Anime: Unknown)


Masumi Sera is at Ramen Ogura with Conan, Sonoko and Ran. Katsumasa Ogura asks Masumi (mistakenly calling her "Mari") if she's going to take the same food to her apartment again. Conan implies that Masumi could be giving food to someone she's letting stay in her apartment, making a clear reference to the child, but she jokes saying that it's for her secret boyfriend. At the end of the case it is revealed that Ogura had found a handkerchief that Masumi had left behind that said "Mary" on it in English. Ogura had confused the English name with the Japanese name "Mari". Conan believes that the handkerchief may be related to the child as well.

Department Store Stabbing Case (Manga: 939-941, Anime: Unknown)


Conan thinks about the child, "the little sister from outside the domain looks a lot like Sera, no wait, more than that girl resembling Sera..." (領域外の妹と名乗る… 世良によく似た… いや…　あの子世良というより…‥ ). Conan also thinks to himself that the child's name is probably Mary. At the end of the case Haibara tried to wipe some of the makeup off of her face in the bathroom, but she missed some just below her left eye. The left over makeup made it look like she had the same eye bags as Shuichi, Masumi, and Mary. This causes Conan to make a connection between her and Mary.

Movie 18: Dimensional Sniper
She is only shown two times at dawn under her hotel bed's blankets.

Identity
The child's relationship to Masumi Sera is mother and daughter. Masumi testifies that she has two older brothers: Shuichi Akai and Shukichi Haneda. Masumi only started claiming to have a "younger sister from outside the domain" after the unknown child coached her to use that cover story if Conan asked about her. She says her father is dead, and her mother lives overseas. Masumi says she doesn't have any more relatives close enough to depend on. She is currently being financially supported by a friend of her father's. If Masumi has told the truth, minus what she said about having a "younger sister from outside the domain", that leaves relatively few options for the child's identity assuming the child is related by blood somehow to Masumi.

The child is an adult shrunken by APTX 4869
The unknown child acts like an adult despite apparent middle-school age. When Masumi and the child speak, the speech honorifics are not those appropriate for an elder Masumi talking to a younger girl. Instead, they appear to indicate the two are on equal levels, or even reverse with the child expressing greater seniority.

The secrecy surrounding the child and Masumi's attempts to get her to trust Conan, whom Masumi knows is a shrunken Shinichi, might be indications that Masumi is trying to get the child help about an APTX 4869 problem. At that point in time Masumi did not know Conan has relations with any of the other Akais, including Shuichi.

The child appears to be sickly and is often seen coughing. This could be a side effect of the ATPX she may have ingested.

In anime, the voice actor for this character has a deep female voice, which resembles a middle-aged woman.

Akai family mother
One possibility is that the child is the mother of Masumi Sera and Shuichi Akai, shrunk by a drug like APTX 4869. There are currently five known members of the Akai/Sera family: a deceased father, a mother, a son who resembles the father, and Masumi Sera and Shuichi Akai, who presumably resemble the mother. Her eyes and features are similar to those of Masumi Sera and Shuichi Akai as noted by Conan, and so she presumably looks like the mother of the family. Masumi seems to recognize Conan Edogawa to be Shinichi Kudo despite him having such a young appearance, and if she does indeed recognize him she is not surprised by his appearance, which could imply that she is aware of age regression and the drugs which cause it; and perhaps even looking into it because her mother was affected by such a regression.

In anime, the voice actor for this character has a deep female voice, which resembles a middle-aged woman.

The child is the sister of Elena Miyano
This very popular fan theory was born after Gosho hinted that two mother characters are sisters. After it was confirmed the sisters were not the previous most popular choice Yukiko Kudo and Chikage Kuroba, and that the Akai family mother was one member of the sister pair, fan suspicion fell squarely on Elena Miyano as the other mother. Gosho has given evasive answers when asked about Elena and the Akai family mother being related, which is his habit when a fan theory is correct but he can't admit to it.