Nattokinase comes from fermented soybean and is a common food in Japan. If you’ve ever seen Natto, you’ll know that it doesn’t look particularly appealing (I tend to think of a bad cold every time I see it). I have never tried it myself so cannot comment on the taste. However, I found this entertaining video of a guy trying Natto for the first time.
First time eating Natto
After he finishes, I thought he was going to bring it up again
If you do eat Natto, and want some serving suggestions, this lady shows you different ways to eat Natto.
How to Eat Natto