Safety Security Force’s frigate, Ume (PF-9) in 1953.
You can see this flag on the mast.
Now, we can chooge lots of interesting flags on the pole of naval vessels.
However, now we missing one important Japanese naval organization: Safety Security Force’s flag!
It will be good option for US/JP warships.
The Safety Security Force (警備隊) was Japanese coast guard agency established in August 1952.
It was successor of Coastal Security Force (海上警備隊), but different to CSF (it was a section of Maritime Safety Agency), SSF was a section of National Safety Agency that have jurisdiction over both Safety Security Force and National Police Agency. Because of it it has become more military-like, and finally it succeeded to the Japan Maritime Self-Defense Force.
After the surrender whole Japanese military organizations were demobilized but anti-mine warfare section were exception: in that time there were lots of naval mines (and still left in modern times!) and minesweepers were necessary for not only Japanese but also allied nations. Because of it, Safety Security Force had lots of minesweepers inherited from MSA. In addition they received multiple naval vessels for United States (Kusu-class frigate & Yuri-class LSSL) so they decided that they have to use their own flag.
This flag was adopted in November 8, 1952.
It has 7 set of blue and white stripes, and Sakura mark is placed center of the flag.
Supplement: other flags of Safety Security Force & National Police Agency
Substitute flag until SSF’s flag was adopted
Ground conter-part, National Police Reserve’s flag
NPR used Japanese police’s Rising-Sun crest and dove of peace.
Jun’ya Katsume (2018) “History of Building of Escort Ship of Japan Maritime Self-Defense Force”, Ikarosu Publishers