Responses
Of course he should mature but also still be the same way to his sister. You know siblings are always the same. Annoying and stuff lol. I don't want him to be a crybaby at that age too tho. Just that annoying but overprotective brother part of him. It's cute ( I don't have a brother I just have two annoying younger sisters so I really favour brothers in webtoon/manga cause I've always wanted one)
I want the younger brother to grow older (like 17-19 year-old) and behave the same way. It'll be much more fun to see a grown-up version of him insulting her but also having a sister complex at the same time. At that time I'm pretty sure he'll be a good Emperor and quite popular among the ladies as well. And when others see him behaving this way for his sister, I would love to see their reaction.