The Miyoshi brothers have powerful regenerative capabilities.  They say that taking life is offering salvation, and in them Shungiku sees his own younger self.  Oooka, who knows the old Shungiku, is doubtful he can win the battle.
That's why you're only insects...
Por eso no son más que insectos.
Por eso solo sois unos 
bichos asquerosos.
É por isso que vocês são só Insetos...