Boil the soba noodles in plenty of boiling water.
While the soba is boiling, chop the green onions.
Slice the yamaimo to make 2 rounds (they will be Totoro's eyes), and grate the rest. Adjust the size of the eyes accordingly.
Cut the nori out to make the eyes, nose, and belly pattern. I just cut them out with scissors, but it may be easier if you use a craft punch.
This is how it looked like before I added the grated nagaimo. I put a mitsuba leaf on top of his head and finished off by garnishing with chopped green onions around it.
This is important!! Use only a little bit of the noodles in the center to make a shallow well for Totoro's belly.
Pour in the grated nagaimo into the well. Add the belly pattern nori on top, and it's done.
I guarantee your child will love this. Pour mentsuyu all over! It's a shame to lose the Totoro shape, but the noodles will taste better if you mix it all up before eating.