“plot”

Though, if you want a realistic answer, it’s easier to do things to friends because they aren’t on guard. Like, if you’re facing an MMA fighter you’re not going to get sucker punched because you’re redirecting then to try and hit you. My friend would have a much easier time sucker punching me because he hasn’t ever tried to punch me.

They don’t fight back/use Haki to block like an opponent in an actual fight would.