Representing the functions of the [[red blood cell]], these characters are depicted as the body's couriers, delivering oxygen and carbon throughout the body (as well as nutrients, unlike actual red blood cells).

Their [[uniform]] will often consist of a reversible [[red jacket]] and [[cabbie hat]], as well as a pair of blue [[pants]] ([[shorts]] for females).

Younger versions of these characters are known as [[erythroblast_(hataraku_saibou)|Erythroblasts]].

h6. This tag includes multiple specifically named characters including:
* [[ae-3803]]: Female protagonist of the [[Hataraku Saibou|original manga and anime]] with short red hair, often paired opposite [[u-1146]]
* [[aa-5100]]: Female senior co-worker of ae-3803 with long brown hair.
* [[nt-4201]]: Female junior co-worker and partner of ae-3803 with medium black hair.
* [[aa-2153]]: Male protagonist of the spinoff series [[Hataraku Saibou Black]] with red hair and often paired opposite [[u-1196]]
* [[ac-1677]]: Male friend and co-worker of aa-2153 with blonde hair and seemingly always closed eyes.
* [[po-1076]]
赤血球 赤血球(はたらく細胞)