This is a story that happens inside a human body. One day, as a Red Blood Cell is delivering oxygen and carbon dioxide, she is assaulted by Pneumococci and rescued by a White Blood Cell. To protect the body that’s their world, the White Blood Cell (Neutrophil) chases after the one Pneumococcus who’s escaped. But the enemy has hidden himself in the most unlikely place...

In the middle of a drill, Killer T Cell tosses a subordinate right into Helper T Cell’s office. The two polar opposites start arguing. According to Dendritic Cell, although they play very different roles today, they were actually classmates at Thymus School. Not only that, but they were totally different back then! What was it that developed between these two during their days of enduring hellish training sessions at Thymus School where only two to three percent of cells manage to survive?