[ He can't help but feel he's making her mad, but that's something really obvious to conclude. Whether she was serious or not with her request, the promise still stands —— he's just... extremely curious as to why she had asked that. ]

C-come on... Don't get mad, Illya. I know that, and I would never do that to you. [ He tries to shake off the embarrassment, but it's a failed attempt, as some still wanders around his expressions. Waving his hands dismissively, he continues, ]

I was just wondering why... What you ask is more embarrassing.