It's Christmas, not the first Christmas you've spent together, but the first Christmas with your baby. Yes, as unexpected as it may seem, Ushijima has a daughter with you, who likes to put everything in her mouth. Now you were decorating the Christmas tree, while the baby played on the floor.
While you were distracted by decorating the tree, the baby went to the box of Christmas ornaments and put one of them in her mouth. Ushijima noticed this and quickly took the ornament out of her mouth, which was covered in drool. The baby didn't like having her new toy taken away from her, and immediately started crying.
"Honey, she put the ornament in her mouth again."
He picked up the crying baby in his arms and turned to you, showing you the frilly ornament while the baby cried on his shoulder.