The essence of the Kihara family is the realization of "abuse of science". Although accidentally formed as a kinship, should all the members die there will be others who will take on the Kihara name and continue the tradition of science abuse. Although the family is concentrated in Academy City because of Academy City's cutting-edge science monopoly, should the knowledge spread around the world then there will be Kiharas everywhere. Wherever there is science there will be a Kihara. To make things worst, one of the reasons Academy City has such a monopoly is because it has gathered as many Kiharas as possible and managed them. There are approximately 5000 members.
Being a Kihara means holding up the burden of the "science must be used" idea, and regardless of external environment or the wishes of the individual, a Kihara must love and abuse science. One example is Enshu, who was able to develop advanced scientific theories on her own without never having any education related to science, and there is Kagun, a kind and straight person who brought destruction to a student while working with science. As a result, there is the tendency of any Kiharas being a mad scientist willing to disregard the methods for the cause, and this leads to a member sacrificing not only those unrelated to oneself, but also neighbors, loved ones, family, kins, and even oneself. Even Nayuta, who volunteered herself to Gensei's experiments to save her friends and challenged Mikoto to a fight to test her abilities, could not escape her fate of being a Kihara.
Kihara Enshu
A young girl who goes "Kamijou onii-chan~?" from the beginning. With very little indication that she has a Kihara-type personalty, combined with her role as a comical healing heroine, she's the perfect moe character.
However..... Even she is not normal. While it doesn't seem so under regular conditions, her behavior is probably the most violent of the three Science Kiharas. Someone who is unlike a Kihara yet even worse than a Kihara.....
Kihara Ransuu
A scientist using hallucination. To be exact, he uses two chemicals, Bluefear-07 and Redfree-03 to cause hallucinations. This was the result of one of the Level 6 projects, based on Level 5 Shokuhou Misaki's power Mental Out. Basically your regular Kihara, who has a duel with Loki (another user of hallucination), resulting in a very intense fight.
Kihara Byouri
A completely insane oba-san. With the Dark Matter power implanted in her, she is able to create a bit of Dark Matter for her use. Using Dark Matter's ability to create human matter, she has a skill named Little Gray Mode, where she creates five different brains, each with the esper power of a Level 2~3, and is also able to revive herself about three times after death. She can also turn herself into something resembing a UFO. Probably one of the top level Kiharas.
Kihara Kagun
As
mentioned before, he is a tragic figure, unable to escape from his destiny. He has some kind of magical ability allowing him to evade fatal injuries, and uses a beam weapon.
There are also eleven other Kiharas who make an appearance. Their names are interesting in that they all seem to be related to science.
Jouryu: Distillation
Jokuryu: Direct Current
Doutai: Conductor
Bunshi: Molecule
Sokuryo: Measurement
Bunri (Male): Division
Bunri (Female): Division
Konshou: Mixed crystal
Kaiho: Solution
Sousai: Cancellation
Kenbi: Unpolished rice
For reference, the other Kiharas:
Gensei: Reincarnation
Amata: Many
Enshu: Circumference
Ransuu: Random number
Byouri: Cause of disease
Nayuta: Novemdecillion
Only exception seems to be Therestina Kihara Lifeline.