Place water and kombu in a pot and let sit for 15 minutes.

Prepare vegetables: trim mizuna, slice carrot thinly, separate shimeji mushrooms, and cut tofu into 8 pieces.

Clean shrimp by rinsing off sawdust and soaking in ice water for 5 minutes.

Remove shrimp heads and shells, leaving the tail and first segment intact. Devein and butterfly the shrimp.

Heat the pot with kombu over very low heat until just before boiling, then remove kombu and add salt.

Add tofu, mizuna, carrot, and shimeji mushrooms to the pot. Cook for 5 minutes until vegetables are tender.