Renkotsu (煉骨, Renkotsu?) is the second in command and is the third strongest member of the Band of Seven. An expert military engineer, he creates explosives and incendiary devices, including a type of flaming oil that he can spew from his mouth, and reconstructs Ginkotsu into a living artillery weapon that resembles a modern tank. He is also a gifted strategist and has some skill at hand to hand combat, although the only members of the group he surpasses in fighting skills are Mukotsu and Kyoukotsu.