I'd like to see more of him. The joke about brothers teasing their sister or the other way around through various ways in front of their friends never gets old for me. Plus, he's just one of those characters that I can't see any way of disliking him.
This is one of those times where I prefer honorifics untranslated. This way I don't know if he's an onii-san or an onii-chan or what. I'd expect -san, but you can't be sure.
The funny thing about these stories is that the illusion that male lead is shota compared to female lead is that no one jokes about the FBI or the police. Only loli arouses these jokes?