Episode 20

"Cancer Cell II (Part I)" (がん細胞II（前編)) is the twentieth episode of the Cells at Work! anime.

Synopsis
Cancer Cell reappears, and harmful bacteria wreak havoc on the intestinal environment. With the body in unprecedented danger, White Blood Cell and his comrades fight to protect the future.

Returning characters

 * Cancer Cell
 * Natural Killer Cell
 * U-1146
 * Killer T Cell
 * Regulatory T Cell
 * Normal Cell
 * Lactic Acid Bacteria
 * Goblet Cell
 * Intestinal epithelial cells
 * AE3803
 * Platelet Division