Cut the bamboo shoot tip in half lengthwise, then slice thinly with the cut side down.

Drain the canned mackerel and roughly flake the fish.

In a pot, bring water and dashi granules to a boil over medium heat. Add the mackerel and bamboo shoots, cover, and simmer on low heat for about 3 minutes.

Turn off the heat and dissolve the miso into the soup. Heat gently over medium heat until just before boiling.