Hataraku Saibou: Kaze Shoukougun

For an ordinary cell, life inside the body is endless routine: divide, work, repeat. One bored cell is therefore delighted when a stranger in a peculiar hat appears and offers something far more exciting than another day of the same labor.

The two begin playing pranks throughout the body, but their harmless-looking fun hides a problem the immune system cannot ignore. As White Blood Cell and the others respond to the disturbance, the bored cell learns that his entertaining new companion may be connected to the body's growing cold symptoms.