One day, while White Blood Cell (Neutrophil) is busy exterminating germs, he meets Backward Cap, a Platelet who wears her cap backwards. She is secretly training to become a stronger Platelet. However, a huge rumbling noise suddenly echoes inside of the body followed by violent shaking.

"Stop it, Cancer Cell!" White Blood Cell (Neutrophil) and his comrades confront Cancer Cell, but Regulatory T Cell obstructs their fight against the enemy! Meanwhile, Ordinary Cell, who had risked his life to save lactic acid bacteria, finds himself in the clutches of harmful bacteria! What fate awaits this world and the cells that live in it?