Although her name means "snow white," Shirayuki is a cheerful, red-haired girl living in the country of Tanbarun who works diligently as an apothecary at her herbal shop. Her life changes drastically when she is noticed by the silly prince of Tanbarun, Prince Raji, who then tries to force her to become his concubine. Unwilling to give up her freedom, Shirayuki cuts her long red hair and escapes into the forest, where she is rescued from Raji by Zen Wistalia, the second prince of a neighboring country, and his two aides. Hoping to repay her debt to the trio someday, Shirayuki sets her sights on pursuing a career as the court herbalist in Zen's country, Clarines. Akagami no Shirayuki-hime depicts Shirayuki's journey toward a new life at the royal palace of Clarines, as well as Zen's endeavor to become a prince worthy of his title. As loyal friendships are forged and deadly enemies formed, Shirayuki and Zen slowly learn to support each other as they walk their own paths. [Written by MAL Rewrite]

In the town of Kurouzu-cho, Kirie Goshima lives a fairly normal life with her family. As she walks to the train station one day to meet her boyfriend, Shuuichi Saito, she sees his father staring at a snail shell in an alley. Thinking nothing of it, she mentions the incident to Shuuichi, who says that his father has been acting weird lately. Shuuichi reveals his rising desire to leave the town with Kirie, saying that the town is infected with spirals. But his father's obsession with the shape soon proves deadly, beginning a chain of horrific and unexplainable events that causes the residents of Kurouzu-cho to spiral into madness.

In the beginning, an "orb" is cast unto Earth. "It" can do two things: change into the form of the thing that stimulates "it"; and come back to life after death. "It" morphs from orb to rock, then to wolf, and finally to boy, but roams about like a newborn who knows nothing. As a boy, "it" becomes Fushi. Through encounters with human kindness, Fushi not only gains survival skills but grows as a "person". But his journey is darkened by the inexplicable and destructive enemy Nokker and cruel partings with the people he loves.

Hikaru Amatsuga's days of tranquility come to a sudden end when he rescues Alma, a mechanical arm crying for help. Alma fuses with his jacket, introducing Hikaru to the world of mechanical arms: mysterious, sentient weapons that normally become a part of their users' bodies. Forced to flee for his life, Hikaru is eventually captured by Aki Murasame, a twin mechanical arms user working for ARMS, an organization that protects the machines against unethical treatment. The Kagami Group, a nefarious organization that treats mechanical arms as mere tools, seeks to recover Alma. Hikaru is deemed a failure by ARMS for his lack of natural predisposition to be an mechanical arm wielder, so Aki is assigned to be his bodyguard. But Aki is defeated by Jun Kagami, who cruelly tears out her two mechanical limbs, condemning the girl to a slow death. Unwilling to abandon Aki to her grim fate, Hikaru miraculously awakens his power and neutralizes Kagami. Now a full member of ARMS, Hikaru is determined to unravel the truth about mechanical arms and protect his newfound friends and allies.