Sweet potato starch noodles (called dangmyeon in Korean) are made from sweet potato starch rather than wheat, creating translucent, slightly chewy "glass noodles" that have a unique bouncy texture. Unlike regular pasta or noodles that can become soft when overcooked, these noodles maintain their distinctive bite and don't absorb sauce in the same way - instead, they're coated with flavours while keeping their characteristic texture. They're naturally gluten-free, have a neutral taste that absorbs seasonings beautifully, and provide a more substantial, satisfying chew that makes japchae such a delicious dish to eat.