puka puka
A yellow apron associated with, but not exclusively worn by, Nagato from Kantai Collection. Canonically says "Puka Puka" on it but many variations exist.
Originates from Danbooru post #1510864 by Shizuma Yoshinori from the official Kancolle doujinshi Teitoku no Natsuyasumi. May in turn be a reference to the earlier work Kurogane Pukapuka Tai which also involved girls and WWII warships, combined with piyo piyo apron.