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. In the spring, she switches to a lab coat with short sleeves.

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.

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.

Etymology

 * The name Mihari (みはり) means "fruit" (み) (mi) and "needle" (はり) (hari).
 * The name Oyama (緒山) means "string" ((緒) (o) and "mountain" (山) (yama).

Anime

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