[They're... in Akito's mind? Despite the light surprise, Setsuna isn't exactly shocked. It's more on that he wasn't expecting it at all.
He thinks to himself, maybe that's why Allelujah and Akito gets along so well. They share a similar trait.
After watching the brothers for a while, his attention eventually floats down to the small grocery bag again. ... No, Setsuna. It's your fault for not buying one for yourself. You can't take Akito's groceries! You can't, you can't—
. . .
Within the next second, he's already pointing at... one of the milk cartons there. A little flustered.]