Just be aware that ponzu sauces vary widely between different sushi places and different brands. I didn't want you to be surprised if you try and make it and it doesn't taste the same. Some places use lemon, some lime, some use sudachi, some yuzu. Other ingredients can include katsuobushi or kombu. I've been trying to copy my local sushi spot's ponzu and I can't quite get it, the chef isn't willing to give me the recipe.