[ Fractional hesitation; then he takes off his as well, smiling more. ] You're too kind. [ His Britannian has an accent, a mild one that sometimes sounds sort of vaguely American, sometimes sort of vaguely English... but his Japanese is Tokyo-dialect, Tokyo-accented. Nothing remotely foreign-sounding about it, really. ] I've been studying for a long time, but it's no substitute for being a native speaker.
So I appreciate the practice. [ Even more ingratiating! ] I'd be happy to give your ear a break, anytime you like.
[ Considering how to phrase the obvious question... ] Might I ask who Ai-san is?
[ It's too bad he doesn't have any excuse to break out his keigo. Desu-and-masu forms are probably as formal as she'd like him to get... since they're already on a first-name basis. ]