I wanted to let you know that its a fairly normal reaction. These noodles are VERY high in fiber and its common for that to create bowel movements like this - they dont get digested because of the fiber content.
I live in Japan, and obviously these noodles are Japanese and here they are known as a "stomach broom", literally because they go through your stomach and clear everything out. Japanese women especially eat these noodles very regularly to stay slim or lose weight. And Its easy to see why - with just a few calories and no carbs! Amazing!!!
For next time you eat them - starting with small amounts of this and working your way up will give your body time to adjust to the HUGE amount of fiber.
However just to be on the safe side make sure that ...
1. You rinse the noodles thoroughly first before use. I sit them in a collander and let them sit under the water for a good 2 or 3 minutes.
2. You then boil them for a few minutes before eating.
The fishy water that they are packaged in can sometimes cause tummy upsets, however as I said this sounds pretty normal
I LOVE these noodles - such a good alternative to pasta. I hope your negative poop experience doesnt put you off!!!