In chapter 5, pages 5, 6, and 7. The little boy with the light hair looks like the main character and has a similar personality. It might not be him, but I think it is (the author made a point of making that character's face very visible- especially at the top of page 7). :)
You're welcome. :)
I said this elsewhere in another comment thread, but
the mangaka suffers from "same face syndrome" which is why Shiraichi-san (the regular customer of the restaurant) and Tatsumi-san (Shinobu's bae) and actually, Shinobu himself, look an awful lot alike.
Don't get me wrong, they're gorgeous and the art style is beautiful but there's not much variance between characters which is a problem and many other mangaka are guilty of it.
There was even a few panels where Tatsumi-san's hair wasn't colored black and I mistook him for someone else, like the child from primary and Shinobu.
It looks like the two of them knew each other briefly as children. I thought that was such an adorable thing to add.