An October 8, 1940 short clip from the NHK news collection featuring university student pilots of the "Kaigun Yobi Kokudan" (Navy Reserve Air Group) of the IJNAF. This particular group was based in Otsu city, Shiga prefecture and is seen flying Yokosuka K4Y1 Trainer Seaplanes from lake Biwa.
Visible civilian registrations are: J-BBPJ, J-BEHD, J-BBPZ and J-BEHC.
Notice that curiously the J-BBPJ registration is not included in the online civilian register or the very latest brilliant "J-BIRD" book.