Chop the mochi into roughly 8 pieces. Be careful when chopping and make sure no pieces end up shooting off and ending up on the floor.
Grill until the mochi begins to puff and turn golden brown. In the meantime, chop up the spring onion and grate the daikon. Gently drain the daikon in a fine-meshed sieve.
Using chopsticks, stir in the sauce sachet to the natto (if your natto doesn’t include sauce, use 1 tsp of soy sauce instead). Arrange the mochi on a plate, stir together the daikon and natto then serve on top and garnish with spring onion.