'K-2' was a Japanese unrealised naval plan for the bombing of the harbour facilities and other installations of Admiral Chester W. Nimitz’s US Pacific Fleet at Pearl Harbor in the Hawaiian islands group using Kawanishi H8K 'Emily' flying boats (May 1942).
Nimitz was aware of the Japanese use of French Frigate Shoals, and thus stationed two destroyers and a supporting oiler of his Pacific Fleet at the shoals to deter these Japanese activities. The Japanese submarines I-174 and I-175 reached French Frigate Shoals, where they found a US seaplane tender, and 'K-2' was therefore cancelled. Another submarine, I-171, arrived on station off Kwajalein atoll to serve as a radio navigation beacon.
The US Navy sent another seaplane tender and one destroyer to deny the Japanese any use of French Frigate Shoals to the Japanese 'Mi' (ii) forces during the Battle of Midway. At the crucial time that the US naval forces were departing Pearl Harbor for the Battle of Midway, therefore, Yamamoto was completely in the dark as to movement of US major surface units.