Cells at Work! CODE BLACK (はたらく細胞！BLACK,Hataraku Saibō! Burakku?, known also as Cells at Work! BLACK) is a spin-off written by Shigemitsu Harada, illustrated by Ikuta Hatsuya, and supervised by the author of the original, Akane Shimizu.
It was first announced on the Kodansha's Morning magazine official website on May 18, 2018 that the manga will launch in the magazine and in the Weekly D Morning digital manga magazine on June 7. It continues to be published in the magazine weekly until its 10th chapter which was published on August 9, reaching its climax. Then, the manga was continued on the 47th issue published on October 25 with the 11th chapter and released biweekly. As of September 2020, a total of seven volumes have been released. The manga is set to end with Volume 8 on February 22, 2021.
Similar to the original, the series is set in a world of anthropomorphic cells working in a body. It follows a the life of a rookie Erythrocyte, AA2153, and a Neutrophil, U-1196, as they work in a poorly maintained, middle-aged body burdened by issues such as stress, smoking, drinking and the like, causing complications in the cells' work and living environment. Chapters usually consist of the cells having to face an ailment, vice or symptom of an unhealthy lifestyle, and overcoming it with the help of medications or surgical procedures. The series tackles darker content than the original, thus the name 'BLACK'. Beginning with the 11th chapter, the setting transitioned from the first body to a second one in even worse condition, with AA2153 and U-1196 being transported to the new body via a blood transfusion. A third significant character, the Neutrophil J-1178, was also introduced.