Japanese Naval Signal Flag #6—Code "Roku" 最初の6の日本の海軍艦隊信号-名前「ろく」

The Roku or ろく is the Japanese Maritime Flag for the Number Six.  It has a white field with red dexter bend.

The Number 6 Auxiliary Japanese Naval flag is visible with the cover art of this model, Yamato model ship.  It is the flag in between Juliette and Golf.