Good to see the brother finally get called out for his behavior. Being tsundere is fine, but he sometimes take it too far. I do make allowance for him as he is obviously young and inexperienced, but he still needs to learn to treat his sister a little better.
This manhwa is so over the top that George No-Filter has wrapped around the universe to become the voice of sanity... I love it.
Also I hope the name "Dumb" is intended to be a pun on "mute" and in the original korean it's not quite so... I mean I get that Alicia is supposed to be rough around the edges, but I can't tell if the name she picked (and is apparently sticking to) is supposed to sound Oblivious or like Trash-Talk