In chapter 120, Ciel sees two children trick or treating. As he looks at them running away, he suddenly sees himself and Lizzy as young children. This sort of flashback is interesting because most of Ciel’s memories are of the worst times of his life. This one seems genuinely happy.
As he watches the children, he actually steps forward, reaches for them, and starts to call to them to wait.
This is one of the first time we see Ciel actually longing for this past rather than just dismissing it. It’s like he’s telling his young self to stop and not move forward. He’s not just telling himself, however, as he’s also saying this to Lizzy.
Could this be like he wishes he could turn back the clock to a time to both him and Lizzy were innocent and happy? Back before he made this contract and before Lizzy became a part of this cult? He wants them to stop and not move forward to their dark futures ahead.
I wonder if maybe this happened because this case weighs particularly on his mind…
After all, we know that even though this is an extra chapter, it settles just fine in the current timeline and Ciel even mentions being particularly busy because of the problem with Lizzie (thank you to @carmillajo for the translation).
And since many people had the impression he was rather cold-hearted about Lizzie’s situation in the past chapters, maybe this was Yana’s way to tell us that he’s in fact very worried (but he’s not one to show it most of the time) and this is why he’s remembering such sweet memories from his childhood and being almost caught up in them, when it usually never happens.
midnight-in-town 