It is sweet of the people on the Silvana to throw a surprise party for his lord, though he wishes they had seen fit to tell him. After all, as Lord Dio's bodyguard, he should be the first one to know any and all developments concerning him.
It is sweet of them to give Dio presents, too. He hadn't known they would do that, although some of the gifts are decidedly inappropriate. (He makes a note of the wine's vintage, though, just in case.) Seeing his lord gleefully accept such a trifling gift (Goggles? That's the best he can come up with? I would give him gold and jewels, all the stars in the sky, if I could) from one of the few people he hates makes his insides twist with rage.
The cake Lady Alvis made is sweet. Too sweet for him, although he eats a few bites out of courtesy. Dio eats two slices and winds up with icing on his face. (Luciola tries very hard not to imagine licking it off, and fails.)
After the party (just before Dio leaves for his mission with that boy, who Luciola hates despite knowing how irrational he's being), his lord pulls him aside and demands to know why he hasn't gotten a present from him yet. As Luciola opens his mouth to reply, Dio starts kissing him.
Dio's mouth is sweet, too.