After completing each scenario, you'll receive a rank based on various factors: completion time, damage taken, enemies defeated, items used, and infection rate. To achieve an 'A' or 'S' rank, you'll need to minimize damage, complete the scenario quickly, conserve resources, and keep your infection rate low. This often requires multiple playthroughs to memorize enemy placements, optimize routes, and perfect combat strategies. High ranks can unlock bonus content, such as new costumes or gallery items, providing a strong incentive for replayability.
