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Mahiro Oyama

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Mahiro Oyama (緒山 (おやま) 真尋 (まひろ) , Oyama Mahiro) is a former otaku slacker and the brother-turned-sister of Mihari Oyama, having been transformed into a middle-school aged girl by one of Mihari's experiments. She is voiced by Marika Kōno in the anime.

Appearance[]

Mahiro's male appearance as a child

Mahiro's male appearance as a child

Mahiro's appearance as a guy directly before the transformation has never been fully seen. As a kid, his face looked surprisingly similar to how it currently is, but with his pinkish-gray hair being much shorter.

After being transformed into a middle-school aged girl by Mihari, Mahiro's hair now stretches to the middle of her back with a single strand on the top poking up and two longer stands that fall to the front and cover her ears. She is also now slightly smaller than Mihari and gives off the appearance of an extremely cute and adorable young girl. Due to Mihari having replaced all her male clothes, Mahiro is now seen wearing skirts and dresses almost exclusively. Despite this, she rejoices whenever she gets the chance to wear what can be considered boyish-clothing.

As time goes on, Mahiro starts to mature both physically and emotionally. While still cute, her outfits begin to strike a more mature cord through the use of tights and jackets. She grows slightly taller and her bust size also increases allowing her to upgrade to standard bras.

Personality[]

Mahiro used to be a degenerate slacker with a love only for noncon hentai manga with stories of bondage and sex slavery, and staying home playing eroge video games. It was noted that before the start of the series, he hadn't left his house for two years. According to Mihari, Mahiro wasn't always like this.

When they were younger they were very close and got along famously. Mahiro would buy his sister stickers when she asked for them, won her stuffed animals at amusement park games, and even gave her her signature hair clip as a reward for doing well on a test. He stopped making time for her as he got older and her achievements surpassed anything he could ever hope to achieve, as the result of a combination of an inferiority complex next to Mihari coupled with adolescent pressure. Despite this, Mahiro has shown an inherent talent for composing haikus about her everyday life.

After being transformed into a girl by Mihari, Mahiro didn't put up much of a fight, though she did show some initial resistance to going outside, showering regularly, and putting up with all of Mihari's new rules for her. As time went on, her old personality started to fade away and she started exhibiting the personality of an adorable younger sister who loved dressing up and being taken care of by Mihari. The main aspect of her old personality that remained however was her love for video games, and she is seen playing them constantly in her spare time. Overall, the roles of Mahiro and Mihari have since reversed with Mihari taking care of Mahiro rather than the other way around.

At the start of the series, Mahiro hated going outside and felt overwhelmed by large crowds due to spending two years inside her house as a shut-in. Spending time with Kaede and Momiji helped to lessen the discomfort and it eventually disappeared shortly after she was enrolled in middle school. Although it still pops up from time to time, Mahiro gets through it by hanging out with her friends.

After being hit on the head by a box, temporarily losing her memory, and gaining the personality of a little girl in the process, some of this other personality has begun to leak through on occasion. This is shown by actions such as the occasional cutesy expression, taking naps after eating cookies much to Mihari's frustration, and feeling uneasy about the sex-slavery and bondage X-rated manga that she used to devour.

A running gag throughout the series is Mahiro wetting herself due to not reaching the toilet in time, but also due to an occasional fright. Miraculously, during these incidents she is able to keep her dresses or skirts from getting wet, and only her underwear and tights takes the blow. She originally felt extremely unhappy and embarrassed when it happened, but it has happened so often now that she's gotten used to it and it doesn't bother her anymore. This self-confidence has even helped Momiji feel better when she also suffers from similar incidents.

Mahiro, despite being female now, is still shown to be nervous and slightly aroused by being in close contact with girls, especially those who are undressing. She loves seeing Kaede show off her body in a swimsuit, and loved how Asahi smelled while she pulled Mahiro's head into her chest for a hug. Mahiro knows that she would look weird while doing this, so while changing with other girls she tends to look at those of her friends that are flat chested to calm herself down, comparing it to looking at "the desolate beauty of the great plains". This, however, makes her look weird anyway by those she is staring at.

After Matsuri came home temporarily, everyone around Mahiro started to notice how much of a mother Mahiro naturally comes off as due to her caring nature. Mihari, Kaede, and the rest of Mahiro's friends all agree that Mahiro's desire to take care of others and comfort them during times of need make her a natural mother at heart, though Mahiro is dreaded by such a prospect.

Despite multiple occasions where the drug has started to wear off (causing Mahiro's "comrade" to regrow), Mahiro has opted to continue taking additional doses of the drug to remain female. She continues to assert her lost masculinity and rejoices when her "comrade" returns, but has opted to stay female for the time being due to loving all her new friends and her new life. She has ultimately opted for trying to find a balance between her old life and new one.

Relationships[]

Mihari Oyama[]

When they were younger, Mahiro got along famously with Mihari. They would play together, and tease each other as brothers and sisters often do, but they also deeply cared about one another and Mahiro would do his best to take care of her as her older brother. This started to change after it became apparent that Mihari was a prodigy whose achievements began to surpass anything that Mahiro could ever hope to achieve. As a result, he stopped making time for Mihari and became isolating himself in his room, sleeping in past noon and playing video games while never leaving the house for a period of two years before the start of the series.

Despite Mahiro no longer caring what Mihari did, she did still care about her older brother and began an experiment to completely rehabilitate his life and make him a functioning member of society through her "Onii-chan Rehabilitation Project" which involves transforming him into a middle-school aged girl and slowly making her a functional member of society by giving her a new life as Mihari's younger sister. She thus takes pleasure in observing how the experiment is progressing, seeing Mahiro as a lab-rat for it.

Since Mihari transformed him into a middle-school aged girl, their relationship has reversed with Mihari now taking care of Mahiro. Mihari always wanted to have a younger sister, and is now taking advantage of the experiment to live out her long sought after fantasies. This is shown by her dressing Mahiro up in various girly outfits, and baking cookies for her. She also gets extremely excited whenever Mahiro acts cute and feminine, though she does get frustrated when Mahiro starts acting more feminine than she does (and tends to point it out). When Mahiro does something nice for her, or when Mahiro puts in a lot of hard work into something and fails, she bursts into tears showing how much she truly loves her and what she does.

Mahiro in turn adores her older sister now, and the two have become closer and closer, though she is occasionally inconsiderate, especially when distracted by the video games she plays.

Kaede Hozuki[]

When they first met, Mahiro was worried that Kaede would know who she really was, but the two started talking and found that they enjoyed each other's company. As a result, Kaede has become another big sister figure in Mahiro's new life. Kaede is always willing to help out Mahiro if she asks for it, and the two have even started keeping secrets behind Mihari's back. Kaede has even helped Mahiro and her friends cook, bake, and pick out new swimsuits.

Momiji Hozuki[]

When Mahiro first met Momiji, Momiji was dressed in such boyish clothing that Mahiro thought that she was a boy. A connection was formed between them almost immediately, though Mahiro started to get worried about her flustered feelings towards Momiji after someone remarked that they looked like a couple. Mahiro was amazed when she learned that Kaede was Momiji's older sister. She was also shocked, and at the same time relieved, when she realized that Momiji was actually a girl. She was delighted to be called Momiji's friend, and the two looked forward to seeing each other again.

A few weeks later, Mahiro met up with Momiji again when Momiji came to her house with Kaede. Mahiro at first didn't recognize her due to her wearing a skirt that day, but was delighted to see her again once things were cleared up. Mahiro tried to make her room presentable when Momiji come into it, and they subsequently struck up conversations on the merits and drawbacks of wearing skirts. Momiji was shocked to find Mahiro with X-rated hentai manga, but Mahiro cleared it up by claiming that it belonged to her [nonexistent] older brother who was away at college (with this originally having been his room). After they boxed up the manga, an incident caused Momiji to land on top of Mahiro and grope her bust with both hands, much to both of their embarrassment. Despite this, the two still enjoyed each others company and decided to remain friends.

Following a few more incidents where Mahiro visited on Halloween, and Momiji almost discovered that Mahiro was a boy on a trip to a hot spring, the two grew closer and closer. Eventually, Momiji invited Mahiro out to meet her two friends Asahi and Miyo, and the four all became close friends.

Momiji is shown to be very jealous when Mahiro pays any intimate attention to anyone other than her, and this has led her to be strangely competitive with others for Mahiro's attention (particularly with Asahi). When Asahi offered Mahiro a bite of her parfait, Momiji ate it herself and then forcibly fed Mahiro a bite of hers, getting into a battle with Asahi over whose was better. She repeated this when Mahiro offered Miyo a bite of her crepe, force feeling Mahiro a bite of hers. Mahiro noted that Momiji's spirit animal could be the bear since she's so soft-hearted and reliable, but Asahi pointed out that it could also work since she tends to get weirdly aggressive at times (which Momiji ironically proved when she slammed Asahi's head into her desk for saying that).

Momiji is the only one in the group (out of her, Asahi, and Momiji) who's come close to finding out that Mahiro was really a boy. She groped Mahiro's "comrade" by accident while in the hot spring, and immediately became suspicious when Mahiro raced out of the spring. Later that night, she decided to look for herself, but saw nothing as it had disappeared as a result of the new dosage of the feminization drug. That morning, seeing Mahiro react girlishly to a perm given by Kaede put her worries to rest, permanently.

Ultimately, Momiji is considered Mahiro's best friend, and is the one that Mahiro hangs out with most often outside their circle of friends.

Asahi Ōka[]

When Mahiro first met Asahi, she was nervous about going out with two new strangers. Asahi came off as inconsiderate by being brutally honest about what Momiji said about her, but it broke the ice and caused Mahiro to laugh in relief as she no longer had to pretend to be someone she wasn't. Mahiro was relieved and quickly accepted Asahi as a friend.

Mahiro and Asahi are polar opposites in almost every way. Asahi is energetic, adventurous, extremely athletic, and speaks her mind, while Mahiro is subdued, more of a shut-in, lacks strength and stamina, and thinks out what she says. Despite this, the two share a very good relationship. Mahiro adores how honest Asahi is with her feelings, such as telling Mahiro to talk about her games since she looks so happy when doing so. Mahiro in turn sees Asahi almost like a pet, with her regularly rubbing her hair and calling her a good girl while doing so. When it comes to adventures, Asahi tends to drag Mahiro along for the ride. Due to Mahiro's lack of stamina, she gets tired very quickly, though Asahi is still happy to have her along.

Mahiro also enjoys Asahi's innocence, and notes the irony of many things she tends to say that go over her head as a result, which Mahiro is entertained by.

Miyo Murosaki[]

When Mahiro first met Miyo, she was nervous about going out with two new strangers. She was a bit confused by Miyo's Yuri shipping of her and Momiji, but quickly caught on and accepted it as a part of who she was. The two subsequently became good friends.

Mahiro got closer to Miyo when she ran into her in disguise trying to buy Yuri manga at Tachikawa bookstore. She agreed to keep the fact that Miyo was into Yuri a secret (despite the fact that it was already well known), and encouraged Miyo not to be embarrassed of what she enjoys. Miyo has since offered Mahiro a glimpse into Yuri by recommending several issues of titles she enjoys, which Mahiro has come to enjoy.

Mahiro is a bit confused as to why Miyo is so embarrassed about being so well developed, but hasn't pushed the issue. Also, similar to the others, Mahiro is a bit put off by Miyo's idea of romance when it comes to girl talk, though she is thankful that Miyo is so level-headed compared to Momiji and Asahi.

Early Life[]

Mahiro was born twenty years before the start of the series, as the first child of Matsuri Oyama and her husband. The status of his father is currently unknown as he has not been named or made an appearance in the series thus far, and any childhood memories that Mahiro and Mihari have described involving their parents have only involved Matsuri.

Three years later, Mahiro became a big brother when Matsuri gave birth to her second child, a girl that she named Mihari. Mahiro was supposedly very close to Mihari from the moment she was born.

When Mihari was four years old, she was at home with Mahiro when a thunderstorm struck. She became scared and began to cry and call for Mahiro while hugging an Oshima plush toy. Mahiro immediately comforted her and wrapped a blanket around the two of them telling her that it was okay. Mahiro suggested that she get some sleep with him next to her, and although Mihari was still nervous she soon drifted off to sleep.

Three years later, when Mihari was seven years old and just starting elementary school, she, Mahiro, and Matsuri took a trip to Oshimaen amusement park. During the trip, Mahiro played a shooting game and won a prize which turned out to be an Oshima stuffed animal. Mahiro gave it to Mihari who immediately hugged it and fell in love with it. Later in the day, she became sepearated from Mahiro and Matsuri which caused her to start crying until Mahiro found her again.

Six years later, Mahiro started attending high school. Around this time, Mihari began to excel at academics and sports, placing first in her class at the end of her first semester of middle school. By the end of her time in middle school, she had set multiple records in sporting events such as track and field that remain unbroken to this day. Although she was doing all of this to get more praise from Mahiro, all this success had a detrimental effect on him. He soon began to feel inferior due to being negatively compared to her despite her being younger than him, and subsequently began to make less and less time for her. Mihari failed to notice this however, and continued to work even harder in the hopes of being able to spend more time with Mahiro.

Mahiro eventually graduated from high school, but had no academic success or plans for his future. Despondent over never being able to measure up to Mihari, Mahiro began to isolate himself in his room, doing nothing but playing eroge games, reading non-con manga, and avoiding everyone and everything.

Shortly before Mihari started high school, Matsuri accepted a long-term overseas assignment for her company and moved overseas, leaving her and Mahiro by themselves, though she supposedly sent money back for rent and groceries so the two could get by.

On Mihari's first day of high school, she was delighted by how she looked in her uniform and went to Mahiro's room to get him to see her in it. By this point he was already isolating himself with a 'KEEP OUT' sign on the door, and received no response when she tried to talk to him. Mihari started to get worried about Mahiro, as she missed him and wanted to find a way to help him.

While walking to school, Kaede made an offhand remark to Mihari about how using makeup and wearing fashionable outfits can make someone look good and improve their self confidence. This gave Mihari the idea to turn Mahiro into a girl. She then realized that if there was no opportunity for progress, there would be no results. Thus, she got the idea to de-age Mahiro as well. From that moment, her goal was clear: to turn Mahiro into a young girl to reintegrate him into society.

Realizing that she needed funding and research in order to do this, she took several tests that allowed her to skip high school and go straight to college. There, she focused on biology and chemistry where she started the project by developing a drug that would turn Mahiro into a young girl.

The night before the events of "Mahiro's Confusing New Body", Mihari slipped the completed drug into Mahiro's food (drink in the anime) to commence with the project. That night as Mahiro slept, the drug transformed him into a middle-school aged girl.

History[]

Etymology[]

  • The characters for her first name, Mahiro (真尋), literally mean "true" (真) (ma) and "fathom" (尋) (hiro). The author, Nekotofu, has noted that he gave this character this name because it is unisex (i.e. there are both men and women named "Mahiro") and shares the same consonants with her sister's name, Mihari.[4]
  • The characters for her last name, Oyama (緒山), literally mean "string" (緒) (o) and "mountain" (山) (yama). According to Nekotofu, the name comes from oyama, a term in kabuki that refers to male actors who play female roles.[4]

Trivia[]

  • In the original Japanese version, Mahiro refers to herself as オレ (ore), a common first-person pronoun which sounds masculine and informal, sometimes rude or crude depending on the context, but she does so only when she is by herself or alone with Mihari or Nayuta, both of who know that she is actually male. In other situations, Mahiro is more inclined to use わたし (watashi) instead, a pronoun which is feminine or gender-neutral.
  • Although it is revealed that the kanji for her first name is "真尋", her name is almost always written in hiragana, like "まひろ".

Gallery[]

Appearances[]

Manga[]

Anime[]

Sources[]

  1. ↑ Onimai Q&A campaign
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2020 Summer Special Brochure
  3. ↑ 3.0 3.1 3.2 Onimai Q&A campaign
  4. ↑ 4.0 4.1 Onimai Q&A campaign
Onii-chan wa Oshimai! Wiki • Navigation
Characters
Main Characters Mahiro Oyama • Mihari Oyama • Kaede Hozuki • Momiji Hozuki • Asahi Ōka • Miyo Murosaki • Nayuta Tenkawa
Students Male Yuta Sakurada • Minato Senkawa • Takeshi Haijima • Tomoya Kiba • Makoto Kodaira • Hinata Tsukishima
Female Nemu Fujimi • Satsuki Takada • Minori Shiina • Mai Yasaka • Miyako Nagase • Nodoka Fushimi • Aoi Tachikawa • Akira Nakai • Misao Nogata
Teachers Mari Nishinomiya • Rin Minakata • Yuriko Kitahara
University Chitose Azuma • Arika Tachimi • Tsubasa Inui
Family Matsuri Oyama • Kasumi Hozuki • Yu Ōka • Yuya Ōka • Yomi Murosaki • Mr. Nagase • Mrs. Senkawa • Kanata Senkawa
Guild Ponta • Shiori • Lucas • Risachii
Other Characters Idol Stuff Hiyori Hisaki • Raika Nanami • Tsurara Miwatari • Momiji Hozuki • Chigusa Hitotose
Niwasaki Diary Anna Niwasaki • Mrs. Niwasaki
Others Kerori • Truant Officer • Ghost Girl • Nekotofu
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