Arcane begins against the backdrop of the contrast between Piltover (the City of Progress) and Zaun (the Undercity).

Two sisters, Vi and Jinx, live in Zaun with their adoptive father, Vander.

Living in poverty, Vi and her friends occasionally rob Piltover to survive.

One day, a major accident occurs while they are robbing a scientist's house in Piltover, and this incident causes tensions between the two cities to escalate to the extreme.

As Piltover's crackdown intensifies, the resentment of Zaun's residents grows.

The ambitious Silco emerges, sparking a power struggle within Zaun, and Hextech—a new technology combining magic and science—is introduced for the first time.