Mihari Oyama

Japanese:
緒山おやまみはり
Romaji:
Oyama Mihari
Birthday:
April 22
Age:
17 (Start of the series)
18 (present)

Gender:
Female
Hair color:
Dark brown
eye color:
Brown
Height:
154 cm (5'1")
Weight:
47 kg (104 lbs)
Blood type:
AB

Mihari Oyama (緒山おやま みはり, Oyama Mihari) is a child prodigy and the younger sister of Mahiro Oyama. After skipping several grades to attend college, she developed a drug that turned her older brother into a high school girl as part of her "Onii-chan Rehabilitation Project".

Strange creatures
Annoying his brother/sister Mahiro
Spending time with your friends
Experiment

College Student at University (current)
High school student at Yotsuba University Affiliated High School (former)

Mahiro Oyama (brother) ("sister")
Matsuri Oyama (mother)

Kaede Hozuki
Chitose Azuma
Arika Tachimi
Tsubasa Inui

Mihari is a high school girl with a very athletic and slender figure. She has dark brown hair tied back with red bows forming long pigtails (in the anime, these pigtails also contain purple streaks). She also has additional hairpins along the sides of her face and bangs, the middle bangs containing a golden hairpin that Mahiro once gave her during her first year of high school as a reward for doing well on an exam. She is almost always seen wearing a red button-down blouse and a brown skirt with a brown belt around her waist and a golden medallion around her neck. She also almost always wears a white lab coat on top of her outfit wherever she goes, regardless of the social situation. In spring, she dons a short-sleeved lab coat. Despite having outgrown her high school uniform, she is shown to still be small enough to barely fit into it, indicating that she hasn't grown much since then.

Mihari is an intelligent girl whose world revolves around her research and her brother. She took exams in her first year of high school and was able to advance to university, displaying high intelligence. Ever since she was young, Mihari dotes on Mahiro. The two were once as close as any brother could be. He protected her and gave her rewards for doing well, which drove her to excel. Although Mahiro began to isolate himself after feeling inferior to her, Mihari never stopped caring for him and began her research specifically to make him a functioning member of society again. Mihari has since taken on the role of an older sister to Mahiro, fulfilling a long-standing wish to have a younger sister. She pampers Mahiro and pushes her into situations to prevent her from reoffending. All of this has brought the two closer together and renewed their close relationship. Mihari now looks forward to being the caretaker, and as such, cries with happiness when Mahiro does something nice for her like he did when they were younger. Mihari is also afraid of thunder, a trait she shares with Kaede. When she was younger, Mahiro would always comfort her by sitting close to her wrapped in a blanket.

Despite her intelligence, a running gag is Mihari's lack of fashion sense, as well as her inability to live up to her own ideals. She has pressured Mahiro to dress in a more feminine manner, but she fails to do so. She wears the same outfit constantly and shows no skill in dressing herself even if she does help Mahiro with it (though this has been shown to be partly due to her own idea that she looks terrible in cute outfits despite everyone's attempts to convince her otherwise). This has led to Mahiro asking Kaede for help, to no avail. Mihari also has no tolerance for alcohol and drinking even a small amount (or even just sniffing a bit) will cause her to become instantly drunk, after which she begins kissing every girl nearby. A single sip of a low-alcohol drink on New Year's Day got her drunk and left her kissing Mahiro, Kaede, and (supposedly) Miyo on the lips. Later, he began kissing his lab partners Arika, Tsubasa, and Chitose after smelling the scent of sake. In a strange way, everything he has done in life has happened because of Mahiro. Even after Mahiro began isolating himself in his room, Mihari wanted to find a way to help him. After Kaede mentioned how makeup and fancy clothing can help someone feel better about themselves and gain more confidence, Mihari came up with the idea of ​​turning Mahiro into a girl as a way to reintegrate him into society. Soon after, he took Advanced Placement tests in order to advance to college and begin research that would allow him to achieve his goals, ignoring any other friends or social positions he would have otherwise enjoyed. This shows how much Mihari has always cared for Mahiro, as his entire life has revolved around her.

Mihari was born seventeen years prior to the start of the series, as the second daughter of Matsuri Oyama and her husband. The status of her father is currently unknown, as he has not been named or appeared in the series so far, and any childhood memories Mahiro and Mihari have described involving their parents have only involved Matsuri. When Mihari was four, she was at home with Mahiro when a storm blew up. She became frightened and began crying and calling out for Mahiro while hugging an Oshima stuffed animal. Mahiro immediately comforted her and wrapped the two of them in a blanket telling her it was okay. Mahiro suggested she get some sleep with him by her side, and although Mihari was still nervous, she soon fell asleep. Three years later, when Mihari was seven and just starting elementary school, she, Mahiro, and Matsuri took a trip to the Oshimaen amusement park. During the trip, Mahiro played a shooting game and won a prize which turned out to be an Oshima plush toy. Mahiro gave it to Mihari who immediately hugged it and fell in love with it. Later that day, she got separated from Mahiro and Matsuri which made her start crying until Mahiro found her again.

Six years later, Mihari began attending Yotsuba University Affiliated High School during the same year that her teacher Mari Nishinomiya also began working at the school. She quickly became friends with a girl in her class named Kaede Hozuki. When Mihari did well on a test, Mahiro gave her a hairpin as a reward and Mihari immediately fell in love with it and decided that she needed to do it more often to get more praise from Mahiro. The next day at school, Kaede noticed Mihari wearing the hairpin and Mihari explained how she got it. Mihari asked Kaede if she had any siblings and Kaede mentioned that she had a little sister. Mihari said that was wonderful and said that if she had a little sister, she would strip her down and dress her up in all sorts of outfits. Kaede pointed out that it only works like that if the little sister likes what you choose for her since her sister was a tomboy and couldn't do that. However, Kaede added that her sister was awfully cute and added that she bakes cookies for her and stuff. Mihari was surprised that Kaede knew how to cook and asked her to teach her, and Kaede agreed. Mihari then suggested that they do it that day after school, much to Kaede's surprise. Mihari smiled, thinking about how happy Mahiro would be once he tasted the cookies. Baking cookies for Mahiro soon became her regular hobby after this. Shortly after this, Mihari joined the high school track team.

Sometime after this, Mihari met up with Kaede at the Neon to buy clothes. She apologized for keeping her waiting, though Kaede was shocked by the fact that Mihari was wearing sweatpants under a skirt. Mihari said that she was doing so because it was so cold today and claimed that everyone at school was wearing them. Kaede claimed that she couldn't wear stuff like that out and about and pulled her pants down much to Mihari's surprise. Mihari asks why she did that with so many people around, but Kaede insisted that she was the one who should be embarrassed. She asked Mihari how she could be so clueless about fashion, to which Mihari pointed out that that was why she asked Kaede to help her. Later, the two of them walked out of the store in new clothes. Mihari called Kaede a lifesaver and said that she would have never known where to start. Kaede realized that even Mihari has things that she's not good at. She commented that Mihari ended up getting a super cute and girly outfit today and asks if that's the kind of thing he likes. Mihari says that it's what her older brother likes, and explains that they were going on a trip together soon and that she wanted something in return. Kaede understood and commented that she's sure he would like it. Mihari said that she hoped so. Back at home, Mihari tried on her cute new outfit and looked at herself in the mirror. She wondered if it was cute, but also thought that, looking at it in the comfort of her own home, it looked a little over the top. She wondered if she could wear it in public and decided that she would die of embarrassment. She decided that she couldn't wear it during the trip and banished it to the back of her closet.

Around this time, Mihari began to excel in academics and sports, ranking first in his class at the end of the first semester of high school. By the end of his time in high school, he had set multiple records in sporting events such as track and field that remain unbroken to this day. Although he was doing all of this to gain more praise from Mahiro, all of 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 devote less and less time to her. However, Mihari was oblivious to this and continued to work even harder in hopes that he would be able to spend more time with Mahiro. Shortly before Mihari began high school, Matsuri accepted a long-term assignment abroad for her company and moved abroad, leaving her and Mahiro alone, though he supposedly sent them money for rent and food so the two could survive. On Mihari's first day of high school, she was delighted with her uniform and went to Mahiro's room to let him see her in it. At that time, he was already isolating himself with a "DO NOT ENTER" sign on the door and received no response when she tried to talk to him. Mihari began to worry about Mahiro as she missed him and wanted to find a way to help him.

While walking to school, Kaede made a casual comment to Mihari about how using makeup and wearing fashionable clothes can make someone look good and improve their self-confidence. This gave Mihari the idea to turn Mahiro into a girl. He then realized that if there were no opportunities for advancement, there would be no results. Thus, he also came up with the idea of ​​making Mahiro older. From that point on, his goal was clear: to turn Mahiro into a young girl in order to reintegrate him into society. Realizing that he needed funding and research to achieve this, he took several tests that allowed him to skip high school and go straight to college. There he focused on biology and chemistry, where he started the project developing a drug that would turn Mahiro into a girl. The project eventually caught the attention of Mihari's faculty advisor, Chitose Azuma, who made key contributions to perfecting the drug. Although Mihari believed she did this out of the kindness of her heart, Chitose actually has a secret agenda that she wants to see carried out through the project as well. The night before the events of "Mahiro's Confusing New Body", Mihari slipped the drug into Mahiro's food (drink in the anime) to get the project started. That night, while Mahiro was sleeping, the drug transformed him into a high school girl.

Her first name, Mihari, means "watchman" (見張り) (mihari). The name also shares the same consonants with her brother/sister's name, Mahiro.
Her surname, Oyama, means "rope" (緒) (o) and "mountain" (山) (yama) when interpreted literally. According to author Nekotofu, the name comes from oyama, a term in kabuki referring to male actors playing female roles.

In the original Japanese version, Mihari refers to herself as わたし (watashi), a common first-person pronoun often used by women.
Mihari calls Mahiro "onii-chan" (お兄ちゃん), which is a somewhat cute and casual way of calling the older brother, if no one else is around. When there is someone else listening to their conversation (also when she makes fun of Mahiro becoming more and more feminine), she avoids calling her that and instead uses "Mahiro-chan" (まひろちゃん) to avoid confusion.