They reach the escalators right as she asks him that and Shiro just blinks his eyes as he looks up and catches the real sight of the sheer height they are going to have to ascend to, the clothing store they are going to being located on the very top floor of the mall. Heights have never scared him in the past. In fact every time he was able to go with his parents on their trips, Shiro loved to look out the window as the plane was taking off and as far back as he can remember he's always done that. So he's not real sure about what exactly is rattling his nerves facing the 4 story height in front of him. Shiro just shakes his head a couple of times though, thinking to himself that the way he's feeling right now will pass sooner or later, as heights have never bothered him before. And then after taking a couple of breaths he nods to Haruhi and says "Yeah..I'm alright sis.."
Meanwhile, Tamaki hearing Haruhi say she doesn't know Carter turns to his direction. It becomes clear to Tamaki instantly, before he even opens his mouth to speak to the kid, that Carter is real nervous. He approaches Carter, to which Carter just stops and stands still and breathes in and out a couple of times himself seeing Tamaki steping over to him, and Tamaki says "Hey there kiddo. Just relax. Everything is fine I promise. What's you name? Are you lost?"
Carter "No..I'm not lost. And my name's Carter."
Tamaki "Where are your parents then? Are they nearby?"
Carter "No they're not here at the mall. My parents are at home."
Tamaki blinks his eyes and looks to Haruhi and then says to Carter "You mean you're here by yourself little guy?" He then sighs as he kneels to the kid's level and says "You know..that could be very dangerous in this big of a place kiddo..Especially for someone of your age.."
Carter gulps nervously and says "Well not exactly..I mean I'm not by myself..My older brother is here..But he doesn't know that he's my brother..My parents never told him about my being born.."