Mihari Oyama

Mihari Oyama (緒山 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 a bright girl who's 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. This has led to Mahiro calling on Kaede to help her to no avail. Mihari also has no tolerance for alcohol as 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.

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

 * The name Mihari means "deep" (深) (mi) and "beam" (梁) (hari).
 * The name Oyama means "string" (緒) (o) and "mountain" (山) (yama).

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
 * Mahiro and the Photo Albums

Anime

 * Mahiro's Confusing New Body
 * Mahiro's Time of the Month