Kirihiko Kirishima is a fourteen-year-old female and genius assassin of Kirishima clan who belongs in Akuu Company. She is also known as "Guillotine" and "Kirihiko LXVI of Kirishima". She moves around the world for her duties. She is a virgin.
She has a blonde hair with a pigtail tied with black ribbon and a fringe on the left side of her head. The black ribbon tying her pigtail is featured as her characteristic symbol. She puts large scarf on her shoulders and wears blue shorts, knee-high boots and black socks reaching under her knees and jacket which consists of white sleeves whose blue portions with red stripes at the end of each sleeve and blue body. In OVA, she also wears bikini with the scarf although unsuitable or unnecessary for swimming.
She has naive aspects in which she had squashed the arm of Shinkuro who was confused by her name "Kirihiko", because the name sounds manly, into her breasts although in street and she had noticed Shinkuro that she is a virgin in an obscure ally of the street. In Kirishima clan, the one who is the strain of Kirishima and succeeded as an assassin gains the name "Kirishima". So, she might have a former name but the former one is unknown. She has an appellation to be called as "Kirihiko-chan" by Shinkuro and she considers it "cute". She alleges that she fluently speaks English but actually speaks awkward. She is feeble to heat and coldness. And she also has pollen allergy and a heat-feeble tongue. Therefore, she considers the Earth as her "enemy". She is a dab hand at fighting arcade games and when she met Shinkuro, then she consecutively accomplished 50 defeats. She is usually a taciturn gamer. But when she takes blades, she dramatically changes to verbose and very militant even though fluently speak English within slang and her terms also become manly with a male pronoun "ore". So, she usually inclines to avoid to take blades in streets. When she fights as an heir of Kirihima style, she introduces herself as "Kirihiko LXVI of Kirishima" before fighting. She is a superior genius of treating blades in Akuu Company and easily defeated strong swordsmen. Even if taking cheap blades, she could easily defeat and beheaded strong swordsmen momentarily. Therefore, her dexterous treatment of blades brought her another name "Guillotine", although she is just an ordinary girl who dexterously treats blades. Else swordsmen including Lin Chengshin hates her because "Kirishima is the enemy of swordsmen, the odious one for all swordsmen dedicating to swordsmanship.". She can distinguish blades whether good or bad. But she doesn't cling to blades themselves. So, she had even thrown away Lin's "Bizen Osafune" into dustbin at the end of battle. She also changes her personality by something slashable such as bamboo leaves or hair even if without blades.
She had originally contempt Shinkuro as worthless to fight. But after Shinkuro easily defeated Frank Blanca as Senki triggered by Murasaki's talk, she considered him as worth to fight and wanted a duel. Although, she left without duel because Shinkuro's peculiar personality which nearly forced her to help rescuing took her off the motive of duel. And she criticises Shinkuro that "You are a nice guy.". In "Princess of Yugamisora", the fourth volume in new cover edition, she angered Shinkuro who didn't fight her but fought Zena and promised for rematch. Then she also promised him that if she wins, she assigns him as an underling and if she loses, she becomes his sweetheart. She indicated her affection towards Shinkuro. When Akuu Company was assaulted and she encountered Shinkuro and Misora, she joined Shinkuro and Misora for fighting while looking for Black Knight.
She often plays with Shinkuro and Murasaki. She had cried because Murasaki considered her as "friend" and blushed after hugging Shinkuro and undercover helped them. She stands for them although she belongs in Akuu Company and she is sometimes embarrassed by it.
She debuts at the beginning of the chapter 18 in manga, in which she assassinates some person who she'd to kill. Later on, she seems to play some arcade games and because she accomplishes 50 defeats, a man angers with her. But Shinkuro appears and she quickly moved to hide an alley. Since that incident, Kirihiko makes varied appearances and every time she gradually befriends Murasaki and Shinkuro, she eventually shows him a special affection as she finally falls in love and robs him a kiss. Later on, when the building is collapsing, she understands the notion of friendship and ends up crashed under the rubble. Afterwards, Kirihiko becomes dying down, but in reality, she had survived and she'd not like to face to neither Murasaki nor Shinkuro.
In more recent episodes, she seems more calm and apparently forming bonds of friendship with other people.