Peel taro (satoimo) and slice into rounds. Soak in water to remove the slimy texture.
Peel daikon and slice into rounds. If it’s a large daikon, cut into quarters lengthwise.
Peel carrot and slice into rounds. If you like to decorate the soup with a carrot flower, cut out some of the round slices into a floral shape. If you do so, separate the rounds and flower shaped pieces. You will be cooking round carrot slices with taro (satoimo) and daikon, but these flower slices will be cooked separately.
Add satoimo (taro), daikon, and carrots into the pot filled with kombu water. Start cooking over medium high heat. Right before full boiling, remove the kombu and discard.
Skim off foam (from satoimo/taro) from the surface of the soup with a fine mesh strainer. Lower the heat to medium low and cover with a lid, leaving a gap. Simmer until the vegetables are tender. Add water if too much liquid has evaporated.
Meanwhile, cut komatsuna (or spinach) in half. Start boiling water in a saucepan. If you prepare carrot flower slices, add them into the water. When water is boiling, add komatsuna and cook till tender.
Take out komatsuna and carrot when they are tender and cut komatsuna into smaller pieces. Set these toppings aside for now.
Once the vegetables in the soup are tender, add 3 Tbsp saikyo miso first. Then add 1 Tbsp at a time till you’re satisfied with the flavor. My family likes thick soup so I tend to add more. Add tofu after you mix in miso so you won't break tofu.
Peel the skin of yuzu and flip over to remove any white part. Julienne the yuzu skin.
Use a toaster oven to toast the mochi until puffy. You can also toast mochi over open flame or under a broiler.
Add the soup into a serving bowl first, then place add mochi on top along with the colorful toppings.
You can keep the leftovers in an airtight container or in the pot and store in the refrigerator for 3 days.