Warcross by Marie Lu
Enigmatic young genius Hideo Tanaka changes the world when he invents Warcross, a virtual reality gaming system used by millions of people worldwide. Emika is a tech-savvy hacker/bounty hunter in a near-future New York, trying to make rent money, when she hacks her way into a high-profile international virtual reality sporting event. Her prowess attracts Hideo’s attention, and he makes her a job offer. Someone nicknamed Zero has been disrupting Warcross code and Emika is hired to go undercover as a player in the Warcross tournament to identify the culprit.