[That tone has Kokichi glancing back at Shuichi in return, one brow raising curiously. A rare moment of assertiveness, and saying that he "wants" him to, not that "he should" or "it might help"? He's interested.]

I dunno, Saihara-chan. You were pretty gross smelling earlier. Can you really imagine someone like me smelling like that? I should always smell nice, don't you think? Plus won't Momota-chan be offended if you did something like that with someone like me?

[Or, for that matter, Maki...but it's not exactly a "no". More of a cautious, "are you sure?" Are you sure you really want him joining you for something like that?]