[He does consider that maybe he should not have sprung it on Kaeya like that, but... in the end, he did want it to be a surprise. Of course it does occur to him that regardless of how he had gone about it Kaeya would have never seen it coming anyway. He's just like that.

Once the other man comes back everythihng is ready, and Diluc is waiting. He smiles brightly when his partner enters the room.]

No, of course not. I did it today to keep it from overshadowing your birthday.

[The thought had occurred to him to do it then, but he had decided against it.]

But I promise there are no more emotional shocks in store.