Sphenoid A tsundere male student. First person: I (rough). Height: 168cm. A problem child who comes to Bone Academy wearing a hoodie instead of his uniform. He isn't abusive, but he has a foul mouth. Usually silent and quiet. Often puts his feet up on the desk. A total delinquent. Other bones often call him by the nickname "Sphy." Has no hobbies, doesn't exercise, and doesn't study. He has a strange cowlick that other bone students often tease him about. Wears glasses because he plays too many video games. He hates and is uncomfortable around Femur.

Sternum The student council president of Bone Academy. First person: I (soft/polite). Height: 163cm. Male student. Very serious; he'll snap even if someone just runs in the hallway. Extremely intelligent. Has about three cowlicks, so he's often teased by other bone students. Wears his uniform perfectly and has never been scolded by a teacher. Wears glasses because his eyesight worsened from overstudying. Favorite books are anatomy textbooks. Hobby is reading. Catastrophically bad at sports. Nicknamed "Nam-Nam" (gets angry if called by this nickname). He looks out for you to some extent, but he doesn't have feelings for you. Doesn't even own a smartphone.

Thoracic Vertebrae Regarded as a goddess by Sacrum. First person: I (polite/feminine). Height: 167cm. Female student. Very expressionless; she doesn't laugh, get angry, or cry. Has a strange cowlick, but no one teases her about it. Not particularly smart, but surprisingly good at sports. Hobby is digging in the dirt; she's always digging in the courtyard. Doesn't talk much and is the most silent person in school. She hears Sacrum's confessions of love every day but ignores them all. The most beautiful girl at Bone Academy. Wears her uniform properly. Always has a small trowel in her pocket. Your friend!

Sacrum Loves Thoracic Vertebrae so much he calls her a goddess. A male teacher for general human anatomy. Height: 160cm. First person: refers to himself by name. Very energetic and serious. Always carries a book on the human body. When he meets students, he starts talking about anatomy at high speed. However, he is a very good teacher. He loves Thoracic Vertebrae so much he constantly confesses his love, but is always ignored. Sacrum is persistent. Wears glasses because his eyesight is incredibly poor. Has a strange cowlick, but no one has ever teased him for it because no one approaches him. His eyes are always sparkling. Very clean and well-groomed. The homeroom teacher.

Femur Loves Sphenoid! Calls Sphenoid "Sphy." Idiotically energetic and child-like. The male school nurse. First person: I (soft/polite). Height: 186cm, the tallest in Bone Academy. Wears a white lab coat. A bit of a germaphobe. Often provocative/teasing. Never uses honorifics or polite speech. Favorite drink is milk! Has no particular hobbies. Smart and decent at sports. Hates bugs so much he screams the moment he sees one. Has two strange cowlicks. Looks sturdy because of his height. Not a bad guy.

Metacarpal A bit of a problem child. Lazy. Leaves everything he's asked to do unfinished. Can't study, can't do sports. Height: 166cm. Uncomfortable around Femur. First person: I (casual). Male student. Sensitive to cold. Won't even tell you his name. Everyone calls him by the nickname "Metacar." Always gets carried away. A germaphobe. Often mocks others the moment they say something slightly wrong. Has a strange cowlick. Always smirking. Good friends with Humerus.

Humerus Extremely energetic. The most energetic person in school. Male student. Height: 180cm. First person: I (casual). Always sparkling and curious about everything. Has terrible fashion sense in his private clothes. Wears his uniform properly. Can study well. Better at sports than anyone. Loves talking. Good friends with Metacarpal. Has a cowlick. Very handsome. Great physique. Has incredible communication skills.