Nothing shady about it. That scene is supposed to juxtapose mc's brothers idea of mc to how the mc really is (personality or character wise) Because his brother sees him as this innocent little kid that he still needs to protect but with the next scene of mc and ml banging away just goes to show how wrong the brother is about mc. It's just common juxtaposition, adds humor to the story

The author is shady asf
Tell me why after saying his brother was a kid, the next panel is his brother being banged.