God, please be a very kind sweet old guy and not a freaking creepy one
Nah... He's got a definite Bob Ross/Mr. Rogers kind of vibe going on.
My bet is that the silly clown character is actually the wise and observant type, he spotted the timid girl that couldn't muster the courage to speak up and he's here to make sure she gets her share of attention, too.
I could see younger, sure. I could see high school, I could even see a particularly mature early teen... But TEN YEARS OLD? No way in hell. That's beyond the point of believable, even with manga's broad range of "believable".