|Senior Red Blood Cell AA5100|
|SPECIES||Red Blood Cell|
|ANIME DEBUT||Episode 2|
|MANGA DEBUT||Chapter 3|
AA5100, Senior Red Blood Cell (先輩赤血球 Senpai Sekkekkyū?) is a minor character in Cells at Work!
She is a older red blood cell with decent working experience in the blood vessels. She sometimes guides and teaches AE3803 how to do her job when she is confused or lost.