第12話: 体の変化に伴い、赤血球が新たな訓練任務を引き受ける
2018年9月23日 放送
Red Blood Cell is assigned a new responsibility… To train a new Red Blood Cell! As the senpai, she has to be more anchored and reliable. But while trying to guide the new Red Blood Cell, she makes wrong turns, gets in trouble with the other cells, and things do not go the way she hopes… Meanwhile, there is something happening to the body that could change their world. (Source: Aniplex USA)