Remove excess water from the tofu using a paper towel and cut it into bite-sized pieces.
Drain the oil from the tuna using a strainer.
Mix the natto well together with its included sauce.
Slice the cucumber and carrot thinly; cut the dried seaweed into small pieces.
Place tofu, tuna, natto, cucumber, carrot, dried seaweed, and chives on top of the rice.
Drizzle soy sauce or low-sodium soy sauce and mix everything together.