Hataraku Saibou: Kaze Shoukougun

A mysterious cell wearing a stylish hat appears before the regular cells, who are bored with just the same (cell division) work over and over again, 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?

(Source: Anime News Network)