Mahiro Oyama

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.

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.

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".