Buso Renkin is an anime/manga series written and illustrated by Nobuhiro Watsuki.
- Buso Renkin: Weapons formed from Kakugane that are summoned by the user's will to fight. They are wielded by Alchemist Warriors and humanoid Homunculi, and are the only weapons known to kill a Homunculus.
- Homunculi: Artificial creatures created through alchemy. They are formed when a Homunculus embryo attaches itself to a living creature. When the embryo reaches the brain, it will take it over, erasing the host's mind, and mutate them into a Homunculus, though they can switch back and forth between human and Homunculus form. Homunculi sustain themselves by eating humans, and must eat them to survive. Depending on the DNA used to create an embryo, the Homunculus can either be part animal or part plant. There are also humanoid Homunculus, who look completely human and leave the host's mind intact, though they become much stronger and faster, gain the Homunculus' immortal body, and can wield Buso Renkin.
- Kakugane: A special device used by Alchemists and humanoid Homunculi, which transform into the user's Buso Renkin when resonated with their fighting spirit. The Buso Renkin a Kakugane forms into depends entirely on the user, and someone can summon two Buso Renkin of the same type if they have two Kakugane. Kakugane also grant the wielders a healing factor that regenerates minor wounds in combat, though it's far more effective when the Kakugane isn't being used as a Buso Renkin.