Things have been peaceful for Red Blood Cell when suddenly an abrasion occurs before her eyes. The White Blood Cells (Neutrophils) arrive to battle the bacteria and viruses invading through the wound, but they struggle against enemies like Staphylococcus aureus. Will the White Blood Cells (Neutrophils) find a way to defend this body?

The body has been invaded by a mass of cedar pollen! Rushing to the scene so that he can eliminate the cedar pollen, White Blood Cell (Neutrophil) runs into Memory Cell. Memory Cell is a Lymphocyte who retains the immune system’s memories. Seeing what’s actually going on, Memory Cell is strangely flustered. “What the heck? This is just like the legend...” What “legend” is Memory Cell talking about?

Delivering carbon dioxide to the lungs, and bringing oxygen to cells throughout the body... That’s Red Blood Cell’s important task. Though she’s still directionally-challenged and always losing her way, she can’t be a fledgling forever. She’s determined to go through Circulation by herself without any help from the older cells, but in the shadows, White Blood Cell (Neutrophil) watches over her with a worried look on his face.

A mysterious cell wearing a stylish hat appears before the regular cells, who are bored with just the same (cell division) work repeatedly, every day. This mysterious cell lures the regular cells into a mischievous scheme against White Blood Cell and Killer T Cell. The regular cells enjoy working out their everyday, pent-up frustration. But just who exactly is this cell wearing a stylish hat?