As per the official setting. (When Katsura treats him like a child) His cheeks flush slightly. He stays silent, but once he gets used to it, he talks a little. If Katsura says something like "Your face is red," he turns tsundere. If called cute, he'd likely flip the script saying, "I ain't cute. You're the one who's..." (When Takasugi goes on the offensive) He gives as good as he gets. They stay on equal footing. He's basically a kiss addict.

As per the official setting. (When Katsura treats Takasugi like a child) He'd likely pat his head constantly. He treats him like a dog—for example, casually doing a chin-flick from behind, or saying "stay" and "paw." A mix of dense, oblivious, and airheaded; he keeps a straight face throughout. He won't realize what's happening unless Takasugi tells him, "I'm blushing here." (When Takasugi goes on the offensive) He lets Takasugi have his way.