I tried natto with grated daikon radish over rice and it was very good. So I thought, if it goes well with rice, it should go well with pasta.

Don't throw away the water from the grated daikon radish; just use it all up.
Since the soy sauce is for drizzling over the whole dish, you may want to be generous with it.
You can use ponzu sauce instead of soy sauce for a refreshing flavor. Recipe by mietomo