The year is 2049, and Tokyo is in the midst of dangerous street riots. Dr. Kosugi, a scientist working for A.R.M.A., has created three "mutanoids" - powerful bio-engineered fighters who regard him as their father. When they find out that Dr. Kosugi is missing, they venture into the city's dangerous areas to bring him back and punish those responsible.
Crimson Tears is an action game with role-playing elements. Controlling one of the three protagonists - Amber, Kadie, or Tokio - each with their own strengths and weaknesses, the player explores randomly generated stages, fighting enemy after enemy in combo-based combat. Winning battles earns experience points, allowing characters to level up and become stronger.
Collecting weapon components from defeated enemies and combining them allows for new weapons to be made. Like the characters themselves, these weapons level up, increasing their attack power and reducing the need for repairs. The protagonists also have access to ranged attacks, blocks, and powerful area attacks. It's also important to keep an eye on the temperature meter, as overheating can be a problem.