1. Place a sauce pan on heat, boil water, and drop somen noodles in it. Leave the oven on high, and cook for 4 minutes stirring continuously.
2. Remove from oven and rinse noodles with very cold water.
3. For sauce, in a bowl, add water, mentsuyu, ginger, and green onion. Mix well.
4. In a serving bowl, put some water and ice. Drop rinsed somen noodles in it.
5. Serve somen noodles immediately with sauce.
You can also strain it in a colander with some ice beneath.