Mihari Oyama

Mihari Oyama ( みはり, Oyama Mihari) is the child prodigy younger sister of Mahiro Oyama. Having skipped ahead several grades to go to college, she developed a drug that turned her older brother into a middle-school aged girl as part of her "Onii-chan Rehabilitation Project". She is voiced by Kaori Ishihara in the anime.

Appearance
Mihari is a high-school aged girl with a very athletic and trim figure. She has dark brown hair that is tied up in the back with a red bows forming long stranded pigtails (in the anime, these pigtails also contain purple streaks). She also has additional stands running along the sides of her face and bangs, the middle bang containing a gold hairclip that was once given to her by Mahiro during her first year of middle school as a reward for doing well on a test.

She is almost always seen wearing a signature red button-up top and brown skirt with a brown belt around her waist and a gold 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 the spring, she switches to a lab coat with short sleeves.

Despite having outgrown her middle school uniform, it is shown that she is still small enough to just barely fit into it, indicating that she hasn't grown much since then.

Personality
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 skip ahead to college, showing off a great deal of intelligence.

Ever since she was young, Mihari has adored Mahiro. The two were once as close as any siblings could be. He protected her and gave her rewards for doing well which pushed to excel. Even though Mahiro started isolating himself after feeling inferior to her, Mihari never stopped caring about him and began her research specifically to make him into a functioning member of society again.

Mihari has since taken on the role of an older sister to Mahiro, fulfilling a longstanding desire to have a younger sister. She spoils Mahiro and pushes her into situations to prevent her from backsliding. All of this has brought the two of them closer together and renewed their close relationship. Mihari now expects herself to be the caregiver, and as such is brought to tears of happiness when Mahiro does something nice for her like she did when they were younger.

Despite her intelligence, a running gag is Mihari's lack of fashion sense as well an inability to live up to her own ideals. She has pushed Mahiro into dressing in a more feminine fashion, but she does not. She wears the same outfit constantly and shows no skill for dressing herself up even if she helps Mahiro with it (though it has been shown that this is partially due to her own idea that she looks terrible in cute outfits despite everyone's attempt to convince her otherwise). This has led to Mahiro calling on Kaede to help her to no avail. Mihari also has no tolerance for alcohol and drinking even a small amount (or even just smelling some) will cause her to instantly get drunk after which she starts kissing all girls in the vicinity. A single sip from a low alcohol drink on new-years day caused her to get wasted and let to her kissing Mahiro, Kaede, and (supposedly) Miyo on the lips. Later on, she started kissing her labmates Arika, Tsubasa, and Chitose after smelling the scent of sake.

Mihari is also afraid of thunder, a trait that she shares with Kaede. When she was younger, Mahiro would always comfort her by sitting close to her with a blanket wrapped around them.

In a strange way, everything that she has ever done in life has happened because of Mahiro. Even after Mahiro started isolating himself in his room, Mihari wanted to find a way to help him. After Kaede mentioned how makeup and sharp outfits can help someone feel better about themselves and gain more confidence, Mihari got the idea to turn Mahiro into a young girl as a way to reintegrate him into society. Shortly after, she took advanced placement tests to skip ahead to college to begin research that would allow her to achieve her goals, ignoring any other friends or social standings that she would've otherwise enjoyed. This showcases how much Mihari has always cared about Mahiro, as she has revolved her entire life around her.

Etymology

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

Trivia

 * In the original Japanese version, Mihari refers to herself as わたし (watashi), a common first-person pronoun which is typically used by women.
 * Mihari calls Mahiro "onii-chan" (お兄ちゃん), which is a somewhat cute and casual way of calling one's older brother, if there is nobody else around. When there is somebody else hearing their conversation (also when she pokes fun at Mahiro's becoming more and more feminine), she avoids calling her so and instead uses "Mahiro-chan" (まひろちゃん) so that she doesn't create confusion.

Manga

 * Mahiro's Confusing New Body
 * Mahiro and the Bathroom
 * Mahiro Faces the Mirror
 * Mahiro's Self Image
 * Mahiro Plays an MMO
 * Mahiro's Melancholy Day
 * Mahiro, Even On Heavy Days
 * Mahiro and the Secret Garden
 * Mihari's Wasted Efforts
 * Mahiro's Unexpected Encounter
 * Mahiro Starts Over
 * Mahiro and the Gatcha Game
 * Mahiro and the Girls' Day Out
 * Mahiro and Kaede's Secret
 * Mahiro the Own-Home Security Guard
 * Mahiro Helps Out
 * Mihari and Her Onii-Chan
 * Mahiro Falls in Love
 * Mahiro's Night Alone
 * Mahiro's Wholesome Playdate
 * Mahiro's Little Adventure
 * Mahiro Attends a Party
 * Siblings Share the Kotatsu
 * Mahiro Visits the Salon
 * Mahiro's Panic! At the Hot Spring (Part 1)
 * Mahiro's Panic! At the Hot Spring (Part 2)
 * Mahiro and the Comrade's Return
 * Mahiro's Perm
 * Mahiro the Streamer
 * Mahiro and the Middle Schoolers
 * Mihari's Wardrobe
 * Mihari's Wardrobe Afterwards
 * Mahiro's First Day
 * Kaede's Concern
 * Mahiro's Difficult Class
 * Mahiro's Exciting Weekend
 * Mahiro and Conversation
 * Mahiro's Lunch
 * Mihari's Lunch
 * Mahiro's Final Exams
 * Mahiro the Patissier
 * Mahiro's Twisted Logic
 * Mahiro's Sleepover (Part 1)
 * Mahiro's Sibling Bathtime
 * Mahiro's Sleepover (Part 2)
 * Mahiro's Double Date
 * Mahiro Rings in the New Year
 * Mahiro and the Spicy Kiss
 * Mahiro and the Allure of Bare Legs
 * Mahiro and the Unexpected Guests
 * Mahiro on Valentine's Day
 * Mahiro's "Something"
 * Mahiro and the Guidance of the Stars
 * Mahiro's Surprise Party
 * Mahiro's Final Present
 * Mahiro Pretties Up
 * Mihari and the High School Girls
 * Mahiro's Relaxing Day Off
 * Mahiro's Big Secret (Part 1)
 * Mahiro's Big Secret (Part 2)
 * Mihari's Skipped Grades
 * Mahiro and the Spankies
 * Mahiro and the Gifted Experience
 * Mihari and the Stuffed Animal
 * Mahiro and the Perfume
 * Mahiro and the Full-Cup Bra
 * Mahiro and the Barbecue Secret
 * Mahiro and the Seasonal Attire
 * Mahiro and the Sticker Collection
 * Mihari's Sticker Memories
 * Mahiro and the Sunshine Girl
 * Kaede's Nickname
 * Mahiro and Visitation Day
 * Mahiro and the Parent-Teacher Conference
 * Mahiro and Swim Class (Part 2)
 * Mahiro and the Comrade's Return Again
 * Nayuta's Recent Past
 * Mahiro's Colorful Life
 * Mahiro and the Rainy Season
 * Mahiro and Self-Styling
 * Mahiro and the Little Garden
 * Mahiro and the After-School Fright
 * Mahiro's Cool Head
 * Mahiro and the Strategy Meeting
 * Mahiro's Beach Fun (Part 1)
 * Mahiro's Beach Fun (Part 2)
 * Mahiro's Deep Clean
 * Mahiro's Summer Homework
 * Doujinshi Volume 20 Commemorative Manga
 * Mahiro and the Photo Albums
 * Mahiro's Anime Time
 * Mahiro and the Summer Festival
 * Mahiro Shelters From the Storm
 * Momiji's Panty Problem
 * Mahiro's Weight-Loss Plan
 * Mahiro and the Charming School Festival (Part 2)
 * Mahiro's Masculine Ego
 * Mahiro and the Visible Undergarmets
 * 2020 Summer Special Brochure
 * Mahiro's Cheer Wear
 * Mahiro's Autumn Outing
 * Mahiro's Cosplay Round-Table
 * Miyo and the Enchanted Night
 * Mihari's Research Lab

Anime

 * Mahiro's Confusing New Body
 * Mahiro's Time of the Month
 * Mahiro's Close Encounter
 * Mahiro's New Friend
 * Mahiro Discovers Adventure and Social Gatherings
 * Mahiro Goes Back to Middle School
 * Mahiro's Role-Playing Game
 * Mahiro's First Girls Sleepover
 * Mahiro Rings in the New Year
 * Mahiro Ponders Boobs and Identity
 * Mahiro Pretties Up
 * Mahiro's Future as a Sister