Episode 5

Plot
The Cedar Pollen Allergen arrives in the human body to seemingly cause chaos. They arrive through an eye (visualized as a lake) and start to infiltrate the body via outlets, as the human eyes did not blink in time.

AE3803 is looking at a map again when one of the allergens comes in through a ventilation shaft and surprises her by growing to a large size. She is too scared to react, just as U-1146 comes in and kills the allergen. He then eats the allergen (phagocytic effect) and deduces that it is a cedar pollen, which is not uncommon around this time. While they don't cause illness like bacteria and germs, they do cause trouble. The two have sympathy for the fallen allergen as it did nothing wrong.

Memory Cell soon arrives and tells the legend is coming true. U-1146 tells him that they are not harmful, but Memory Cell tells the two of a legend that has been passed down that they are the "harbingers of doom" and that their appearance will result in the end of their world. More allergen arrive in the body and unintentionally damage the buildings. U-1146 sends AE3803 away and engages the allergens, wondering if the legend is actually true.

B Cell soon arrives from the secretion gland and sprays the allergens with his IgE antibodies, killing them. U-1146 wonders if the catastrophe has been averted and asks Memory Cell if it is over yet. Memory Cell states that B Cell has just stalled it, as the "mist" will turn into "dark clouds that summons a heavy rainfall and sweeps everything away".

In another part of the body, Mast Cell wonders what is causing the increase in the IgE antibodies. She takes a manual and adjusts the histamine distribution. At the battlefield, U-1146 states that too much IgE is not good for the body, which Memory Cell agrees with. He talks to B Cell and tells him to lower the IgE usage, but he states that the histamine will arrive soon. The histamine valve soon appears, but suddenly retracts and a larger nozzle appears in its place, flooding the whole area with histamine.

Not all of the allergen was killed, and U-1146 begins to believe the legend. Mast Cell realizes that the body has been invaded by the allergens, which explained the large amount of IgE. She applies even more histamine, which floods the body and short circuits the secretion gland. This forces the emergency immune system to kick in. As the Neutrophil finish off more of the allergen, missiles are launched to cause sneezing, which fulfills the "disatrophism" part of the legend via nasal congestion. The dam holding the tears breaks, causing the "great flood" and allows more allergens to enter the body.

The normal cells mob B Cell, blaming him for his excessive IgE use. However, he states that the excessive histamine use caused it, so the angry mob drags Mast Cell to him. The two start arguing over who was wrong, which then turns into a brawl. U-1146 notes that even if the cells overreacted, they still had to do their jobs. AE3803 suddenly arrives, running into U-1146 and Memory Cell with a large black ball, quickly apologizing to the two. She tells them that the ball appeared and she was tasked with delivering it to the affected area. Memory Cell did not recall the ball in the legend, and it suddenly opens and reveals a robot that starts to destroy the surrounding area of allergens. Memory Cell then remembers the robot, as it comes when the world changes and destroys everything involved in it; its name being Steroid.

The Steroid soon runs out of battery, ending its destruction. The allergens also died out sometime after Steroid's arrival. Everyone made up with each other, and Memory Cell vows to remember the incident so that it never happens again.

New characters

 * Monocyte
 * Cedar Pollen Allergen
 * Memory Cell
 * Steroid

Returning characters

 * Helper T Cell
 * Macrophage
 * AE3803
 * U-1146
 * Regulatory T Cell
 * B Cell
 * Mast Cell
 * AA5100