“According to the Onigiri Society, one major rice ball trend to watch out for in the future is the “reverse import.” An example of this phenomenon is the California roll becoming popular in Japan. Little was said on precisely what form the reverse-import rice ball might take. It’s hard to imagine it’ll be the British fish and chips onigiri, the Swiss cheese fondue onigiri or the Alpine macaroni onigiri. Available at the Onigiri Summit, all three were part of an “Onigiri of the World” series of rice balls developed by Nico Nico Nori in collaboration with the Osaka University of Arts and to be sold during Expo 2025”
https://www.japantimes.co.jp/life/2024/09/08/food-drink/onigiri-summit-rice-ball-japan/