As soon as they said 'void fist' it sounded familiar. So the older brother is the pretty boy from the martial arts tournament who looked down on heroes?
Side note. If Pig God doesn't count as a monster, why does Amai Mask? There's no physical way for Pig God to be human, considering how we've seen him eat monsters multiple times his entire body in size.
@Kazekid
Maybe he'll do it BY giving a fuck. If they do kill Amai Mask, who Saitama now thinks is a pretty great guy, we might see him finally becoming enraged. Can you imagine how much damage an enraged Saitama could do?