Neba-neba (ねばねば) is the word you'll hear describing these three foods in Japan.
Neba-neba is sticky, gooey, or slimy. These are foods that people tend to either love or hate.
Of course, the stinkiest of the sticky foods to start us off. Fermented soy beans that have sticky strings of goo when mixed or picked up with chopsticks. (Aptly named "String of Strength" in the featured product above.) I love soy products, Except natto. It smells like dirty socks and after trying several times, I usually can’t make myself take more than a bite. As a fermented food, it’s supposedly very healthy, but I’ll stick with kimchi. If you like the stuff, these little packages are affordable and everywhere.
Yama Imo OR Naga Imo
“Mountain Yam” and “Long Yam” (of Chinese origin but almost the same thing, maybe crispier) are root/tuber foods. Not so much related to potatoes, they are probably more like burdock or lotus root. These are peeled and can be sliced (especially for tempura) for a not so slimy serving, or grated. When grated (とろろ), yama/naga imo becomes wet and sticky. It’s sometimes mixed with natto or added to tsuyu, the dipping sauce for zarusoba (cold soba). It doesn’t have a strong smell or taste.
Sato Imo is also slightly slimy, but usually served in soups so we don’t notice it as much.
I was a bit surprised that okra (オクラ) is popular in Japan, but it makes sense. Okra is popular in the south of the US, where it’s often deep fried. That region is also humid during summer, so okra must grow well in humid conditions. Okra is healthy and can be eaten raw in salads or with hiyashi chukka. Perfect during the hot months when it's in season. It can also be cooked in lots of dishes like soups or fried with tofu. When sliced, okra has a super slimy texture, especially the white seeds and surrounding liquid. It can be mixed with foods for a natto-like texture, and is commonly eaten with natto. I’ve heard the seeds can be dried and roasted for a caffeine free coffee substitute, but have never tried it.
I found a special prepared dish in the store today, conveniently titled, ねばねば丼 - "gooey rice bowl." I can see the natto & okra, plus some sashimi (chewy ika for good measure). This was the last one left at around noon. There you have it. Japan's obsession with slimy foods is complete.