I tried NATTO with vinegar and soy sauce. Vinegar seems to make NATOO mild in taste and smell.
I mean AJI-PON (left side in photo) by vinegar and soy sauce.
I also tried NATTO with sugar, AJI-PON and black pepper. It is nice! I recommend it for NATTO beginners.
I will try NATTO with salsa sauce and NATTO with tomato ketchup.