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.

Toxic reaction found on the epidermis! Mast Cell does her job according to the manual, but complaints pour in from other cells that are annoyed by her actions. Mast Cell loses her cool and unleashes her rage... An incident occurs where an unknown entity breaks through a blood vessel and the blood cells get sucked away!

An incident has occurred in the body! The Immune Cells rush to the scene and fight the cells infected by a virus. An Ordinary Cell observes this everyday scene with a bored look on his face and says to himself, "I want to heroically save somebody and have them say to me, 'Thank you for helping me.'" A group of mysterious bacteria appear in front of the Ordinary Cell and...

Ordinary Cell heads to the intestines with White Blood Cell (Neutrophil) to reunite the lactic acid bacteria with their friends, but they get separated from one of the bacteria on the way there. Ordinary Cell desperately searches for the lactic acid bacterium but is attacked by cells infected by a new virus!

The antibody information of a cell has leaked. There is tension in the air after NK Cell makes a comment to White Blood Cell (Neutrophil). The journey to reunite the lactic acid bacteria with their friends takes the group to the large intestine. In the intestine, which has been irritated due to toxic gas being released by harmful bacteria, the group meets up with Memory T Cell who was formerly known as "Killer T Cell."

The most formidable foe has returned... Cancer Cell has reappeared, and harmful bacteria are wreaking havoc in the intestinal environment. With the body being in unprecedented danger, White Blood Cell (Neutrophil) and his comrades fight a bloody war to protect the future of the world they live in.

"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?