That's Lucy's gift to Daisy. Remembering Lucy makes him gloomy
Recap: On Lucy's first day back to school she brought that gift to give to Daisy for her birthday that weekend.
She also said she wouldn't be coming because of having to deal with moving back to Roseville. Seems kind of odd to miss a friend's birthday instead of finding time to unpack elsewhere.
Plus in the last chapter Lucy agreed to go out to the carnival with Paulo despite that her room was filled with unpacked boxes.
On that date Lucy became very aggressive when she learned Paulo was considering not going to Daisy's party, forcing Paulo to agree to go.
The conjecture is she is deliberately staying away but wants all her friends to be present when the box is opened.