This sounds like a fun sequel! Based on the universe,
"I guess you're not as weak as you look... but I'm still watching you."
The brother offers a reluctant fist bump or a "Don't be late for dinner" warning—his way of finally accepting the new friend into the group.
The battle starts with high intensity. Your brother is using his signature stamina/defense moves to shut down your friend's attack types. He’s not just playing for fun; he’s trying to prove your friend isn't "strong enough" to hang out with you.