IJA did not clarify data and Kawasaki only confirms the fact as a maker. General aviation records tell that there was a 15 hour non-stop flight between Japan and Taiwan in 1929.How long was the flight?
Japanese cluster bomb Kurai(空雷).
I have not heard the Kurai but Mk3 bomb for IJN or Ta-bomb for IJA.
Source: Japanese Air Corps during the War(1969)