Sansai is sometimes bitter and other times not but for the most part these are medicinal, many neutral in taste but have immense importance in Japanese cuisine.
Take the yam and use a: https://mesubim.com/?s=Suribachi+ to grind the yam and make it gooey activating the active digestive ingredients. Then you can add some shoyu-dashi and simply add it to the dish with some nori atop, and you have an amazing Sansai dish, none can compare except maybe natto.
While most are wild, some are cultivated or grow wild and one we enjoy to eat is the prized variety wild yam called Jinenjo: https://mesubim.com/2015/01/11/yamimo-mugitoro-gohan/ and one of our favorites: https://mesubim.com/2015/03/23/tororo-nagaimo-potato/
Yamaimo and Nagaimo in the Edo Period (1603-1868) was considered to be an aphrodisiac, and went by the name “mountain eel.” During this period men not only ate Yamaimo, but they also added it to their bathwater to enhance their virility.