Neji wasn't exactly the life of any party, even back home, but now he's especially loath to draw too much notice to himself. But Chouji is a kind person, and has been kind to him during his recent... difficulty, so Neji doesn't feel it right to snub the party, either.

So he slips in, hanging back to the edges of the room as he searches out the guest of honor. He can go give him well-wishes in a quiet moment, and otherwise hopes he simply won't be noticed.