The series is set in a near-future world where the boundary between human being and AI is vague. A rapid biological evolution, similar to "Cambrian Explosion," is caused by one incident. This incident turns into the genesis of a new jostle for supremacy, and the influence of the evolution goes beyond biological framework and spreads to various kinds of materials and technologies. The era of massive evolution involving diverse existences, such as human, machines, and biotechnologies, is coming. Characters fight an existential war in such a world. (Source: ANN)

In the Kagami household, the old Western palm-sized mirror has been passed from from generations to generations. Akko-chan has been taught about the importance of the mirror and when she finally receives it from her mother, she cherishes it with all her might. One day, in the midst of a disturbance made by Taishou and his gang, Akko-chan accidentally broke the mirror. She made a grave and buried the broken pieces in the backyard. That night, Akko-chan was awakened by a flash of light and a kind voice which belongs to the Queen of the Mirror Kingdom. The Queen expresses her gratitude to Akko-chan for valuing the mirror so much and offers her a gift—a magical compact mirror. Whenever Akko-chan sings the magical words, she will transform into anything she wants. (Source: ANN)

Chika Homura begins her high school career with a goal: to develop a "cute girl" persona. After quitting the volleyball team despite her all-star status, Chika decides to join her school's underrated Wind Instrument Club and play the flute, believing it to be the most delicate and feminine instrument. For the first time in nine years, Chika reunites with her childhood friend and total opposite, Haruta Kamijou. Unfortunately for Chika, Haruta is not fooled by her efforts to become more endearing. But this does not deter Chika, and she develops a crush on the band instructor, Shinjirou Kusakabe—but so does Haruta! However, Chika's high school life just won't go according to plan, as mysteries begin appearing around her and her friends. The club members must work together to solve the mysteries plaguing the school, all while trying to find more members to compete in musical competitions. [Written by MAL Rewrite]

Second season of Hangyakusei Million Arthur.