Has anyone ever done clear soup at home?

You'll need seaweed and tofu, which requires you to go to the store, where you might as well just buy the soup.

Just go to the Asian supermarket and buy the instant stuff in packets. That’s what most I expensive sushi joints are serving anyway. Look for instant dashi powder. If you really want to try it from scratch, you will need to go to an Asian grocery anayway. You will need kombu dried seaweed, some katsuobushi (dried bonito flakes), and water. Recipes galore online fro dashi, and that clear soup is usually dashi spiked with a little soy or sake. some places put a few noodles in the bowl, or chopped mushroom and green onion.