The city of Saronica is under attack by an army of monsters called the SMO, who capture the city and rule its populace with an iron fist. The Resistance is formed to stop the SMO, led by a woman named Lily who is kidnapped while trying to help a man named Kou.
Death Crimson OX is a light-gun game where the player shoots at enemies that appear on screen and saves innocents from the monsters. The player can also power-up the "Crimson" pistols by shooting death flowers, which turns their firepower into machine guns to decimate hordes of enemies. There is also a health meter that increases in size with successful enemy shootings, gaining experience points.
The game features a unique storyline where the player must navigate through the city and rescue Lily's daughter, Yuri, while stopping the evil forces within the city.