Prismatic

Humanity has two rules. One, everyone is born with a black armband on their skin. Two, if you aren't, you better find a good way to cover it up. Ekaterina Tolstaya, a college student with a golden armband, makes the mistake of showing her band in public. As a result, she's forcibly taken to a illegal fighting ring. She meets Red, a mysterious woman who stops at nothing to win every fight she encounters. Desperately fighting for her life, Ekaterina realizes that her real enemy is yet to come.