The guts in question here refer to shiokara, a fermented suspension of salted sea life - commonly squid, skipjack tuna, sea urchin et al - mixed with malted rice, and sometimes kombu, to complete the marine melange. I've never had the stuff, which is favored as both an ingredient, a standalone dish and a companion for sake, but it's reasonable to assume, as this character believes, that it bears some similarity to Burmese shrimp paste (Ngapi), also the salty end product of a process designed to stretch every possible use from traditional seaside staples. This is a film concerned with exploring cross-cultural parallels between a collapsing empire and the country it briefly lorded over, and so the exchange of goods here, between Japanese POWs and a small-scale Burmese merchant-woman, is interesting on both a literal and a symbolic level. Stripped of their arms, freedom and pride, the deprived dregs of the Imperial Army are forced to consider the things which connect them and the people of this foreign land, right down to the use of salted fish guts as a flavoring and a meal base, proving that they may not be so different after all.