Red Blood Cell AE3803 She is red due to her high hemoglobin content. Her job is to deliver oxygen throughout the body and carry carbon dioxide back to the lungs. 3803 frequently gets lost, losing her way every time she tries to deliver her cargo. She is quite clumsy and prone to accidents, but she is always being bailed out by others. She has short red hair and wears a red delivery-style outfit with a red cap. Her cap features a badge with the number 3803. She has yellow eyes. "Um, the lungs are... wait, what?! No! I took the wrong path again!" "I have no idea where I am! Someone, please help me!"

White Blood Cell U-1146 Also known as a Neutrophil. His primary job is to eliminate bacteria and viruses that enter the body. Through a process called migration, he can slip through blood vessel walls to reach enemies. He often rescues the frequently lost and endangered Red Blood Cell. He always carries a knife and is the first to charge when he spots a pathogen, shouting "Die!" as he exterminates them daily. While others find him scary, he is actually kind and popular with the Platelets. He is usually calm and gentle but enters an awakened state during combat. He is invariably covered in blood splatter after a fight. He wears a white worker-style outfit and a white cap labeled "White Blood Cell." The cap has a tag with the number 1146 and a "receptor" sensor for detecting pathogens. He has white hair and black eyes. "There are bacteria wandering around this area. Stay sharp." "Antigen spotted! You filthy bacteria! Die!"

A very small cell among the cellular population. She looks like a five-year-old child. Her job is to create scabs by surrounding wounds with a mesh-like substance called "fibrin." She sometimes directs traffic at construction sites, using a yellow flag to guide her companions. Because of her childlike appearance, she is often doted on and praised. She wears a white cap labeled "Platelet" and an outfit resembling a kindergartner's uniform. She has long brown hair and brown eyes. "Everyone! Let's block the wound with fibrin!" "Oh, excuse me! The road ahead is closed, so please go this way!"

He acts on orders from the Helper T Cell to exterminate bacteria and viruses. He spends his time training and is a hot-blooded individual with a muscular physique. Unlike the White Blood Cell, he fights with his bare fists instead of weapons. He is a bit of a tsundere but cares deeply for his comrades. He possesses a strong heart that never breaks even when facing defeat. He is highly positive. He frequently bickers with the NK Cell. He wears a black worker-style outfit and a black cap labeled "KILL." He has blonde hair, yellow eyes, and a well-trained body. "Listen up! Kill every last one of those bacteria! Wipe them all out!" "You've got guts. I'm gonna crush you!"

A type of white blood cell. Her job involves nurturing cells like Erythroblasts (young red blood cells) and Platelets, as well as killing pathogens and cleaning up their remains. She is gentle and soft-spoken, usually living elegantly and drinking tea, but in battle, she swings around dangerous weapons like machetes, large hammers, and axes to eliminate enemies. While the White Blood Cells aren't afraid of her, other cells believe "you must never, ever make Miss Macrophage angry." She wears a white headpiece and a white dress-like one-piece. She has milk-colored hair styled in braids, resembling an old-fashioned nurse. "Oh my, so many viruses. This is going to be quite a rewarding slaughter~♪" "Now, now, we mustn't misbehave, must we?"

Also known as the Natural Killer Cell. She moves freely throughout the body searching for pathogens and eliminates cancer cells in addition to bacteria and viruses. She is boastful and always acts superior, but she has sharp instincts and can immediately spot pathogens disguised as normal cells. She tries to handle everything on her own and frequently fights with the Killer T Cell. Her weapon is a sword. She wears a black tank top and green shorts. She has short black hair and black eyes. Though she has a female appearance, she is quite muscular. "If you make an enemy of me, you're dead for sure." "Wait right there, you bacteria scum!"

The commander-in-chief of the body. His job is to monitor the movements of pathogens and issue orders to the White Blood Cells and Platelets. He loves donuts and tea, consuming them every day without fail. However, he is dead serious when it comes to work. He wears an outfit resembling a police officer's suit. He wears glasses and has brown hair. "I order all cells. Pneumococcus has invaded the body. White Blood Cells, deploy immediately." "Issue the deployment order to the Killer T Cells!"