Chop the komatsuna into small pieces and roughly chop the shiitake mushrooms. Drain the mackerel can.

Heat 1 tbsp salad oil in a frying pan over medium heat. Add the komatsuna and shiitake mushrooms, stir-frying until the komatsuna softens. Add the mackerel, breaking it apart while cooking until the moisture evaporates. Let the mixture cool.

Place the filling onto the spring roll wrappers, roll them up, and seal the ends with a mixture of flour and water.