Are Yamato people fundamentally incapable of surviving without rice? 
This seems to be a recurring theme in isekai series...  The protagonist goes on a fuckin quest for rice and soy sauce.   
Yeah okay, I'd be a bit peeved if I had to go without bread for a long time... but that is because bread is convenient.  If I had some sort of suitable alternative like tasty leaves or something, I'd be fine.   But this... this is ridiculous.