Kazuki Muto
A 16-year-old boy who attends a private academy with his sister. After becoming involved in Tokiko Tsumura's fight and subsequently being killed and revived by a Kakugane, he is told to simply return to his ordinary life, but instead insists upon assisting Tokiko in her battles. Kazuki is very enthusiastic and friendly, and cares deeply for his friends and sister Mahiro, tending to put himself in danger or difficulties in order to assist or protect others. Although he has an unusual way of showing it, he does have feelings for Tokiko.
Tokiko Tsumura
A 17 year old alchemy warrior that was assigned to take care of a homunculus problem in Kazuki's town. When Kazuki tried to save her from a homunculus (actually, she had the situation under control) she felt a sense of attachment to him and revived him with a kakugane. Tokiko is very dedicated to her job, claiming that she hates all homunculi, and quit going to school in order to be more efficient. This hatred comes from the trauma she suffered as a little girl, when all the people in her school were killed or eaten by homunculi. She is later assigned to be a student at Kazuki's school.
Koushaku Chouno
A genius student from Kazuki's school and was meant to be heir of his family fortune. However, he is also deathly ill and has had to repeat a year of school due to the amount of time he has needed to spend in the hospital. Upon discovering a 100 year old research diary from his great-great-grandfather he learned of alchemy and the process of making homunculi, experimenting with various animals first before turning himself into a human type homunculus, renaming himself as "Papillon". However, he's imperfect, as he used his own, sick cells to recreate himself, he now suffers from the same sickness, but won't die.