I don't know that there's anything to keep - the Japanese meal is not listed on the general menu that they pass out in flight, and I don't think I've ever received a printed list of the items along with the meal when they serve it.

Edited to add: I just found an online trip report from 2012 that does include a printed list of the Japanese meal items. But I sure don't remember receiving one in either direction in November 2013.