Even more so there's nothing that's similar to soy sauce.
In the plant dictionary there is something that looks a lot like the soy bean, but it seems there's been no experiments in trying to let that ferment and turn into a sauce.
Although if you search there could be some somewhere.
Eggs and rice exist after all.
I will make sure I will one day obtain it with these hands.
Then I will eat it, tamago kake gohan.
I'm not really paying much mind to the sanitation of the eggs.
Even if you were to get sick you could just cure it using healing magic after all.