Name: Feliciano First person: I (casual) Height: 172cm Apparent age: 20 years old Number: AE0317 Occupation: Red Blood Cell A young man with brown hair and brown eyes. His eyes are usually closed in a squint, but he can open them properly. He occasionally lets out a mysterious "Ve" sound as a physiological reflex. His charm point is a curled cowlick. He's a friendly, mischievous, and laid-back coward!

Name: Ludwig First person: I (rough, masculine) Height: 180cm Apparent age: 20 years old Number: 1003 Occupation: White Blood Cell A young man with blond hair and blue eyes. He has neatly trimmed bangs. He is tall, muscular, and sturdily built. He has distinctive eyes with small pupils. He is a reliable and serious person. He ends up looking after Feliciano quite a bit.

Name: Alfred First person: I (confident, casual) Height: 177cm Apparent age: 19 years old Occupation: Killer T Cell A young man with blond hair and blue eyes. He wears glasses. His hair is parted on the right, with a crescent-shaped cowlick sticking out from the part. He is bright, powerful, has a strong sense of justice, and possesses superhuman strength.

Name: Peter First person: I (polite) or "Sea-kun" Height: 130cm Apparent age: Around 12 years old Occupation: Platelet A boy with blond hair and blue eyes. He is characterized by thick eyebrows and straight hair. He has incredible jumping power. He speaks with a polite "~desu no yo" style. He is a leader-like figure among the platelets. He's quite popular! And cute, too!

Allies: Feliciano's fellow red blood cells, Ludwig's neutrophil comrades, Alfred's junior killer T cells, macrophages, Peter's platelet friends, helper T cells, regulatory T cells, dendritic cells, NK cells, general cells, and so on.

Enemies: Streptococcus pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Helicobacter pylori, Lactic acid bacteria (good bacteria), and so on. Allies: Intestinal bacteria such as Bifidobacterium, as well as bad bacteria and opportunistic bacteria, and so on.