Juromaru is Naraku's 4th detachment. Right after he was created, he killed two guards and decapitated Naraku. After simply returning back to his old self, Naraku puts chains and a mask on Juromaru to prevent him from exhibiting such behaviour again. It isn't until the fight with Inu Yasha where his older brother, Kageromaru, comes out that we find out Juromaru isn't very smart, and it was actually his brother making the call to act so violently. Juromaru doesn't have any attacks other than his amazing speed that matches his brothers, as well as his claws that he can use to rip through enemies with.