Its a bit much to translate, but basically there are a bunch of patriotic slogans, with the names of the people who wrote the slogans written under them. On the top of the flag, separated by a large gap are the words 万歳 (Banzai), written right to left.
In the second photo that Uncle Frank kindly supplied, are written (top to bottom, starting from the right)
滅私奉公 高田胤文 Messhi Hōkō by Takada Tanefumi. It means basically sacrifice yourself for the greater good. It's not a suicide message. It means put away your desires and your ego, and devote yourself to your country.
武運長久 高田忠喜 Buunchōkyū by Takada Tadakichi. It means Good Luck in Battle. This is written also on the left side as well.
愛国 蜜本 Aikoku by Mitsumoto. Just means "Patriotism". Mitsumoto is a very strange last name. I could have the reading wrong.
In other places
必勝 Hisshō (certain victory)
忍耐 Nintai (perseverance)
As always, this could well be a fake. There is a dedication on the far right of the flag, but I can't read it. Its scribbled rather poorly. Looks kind of like it says "To my/our older brother".
Thank you Uncle Frank for you time and dedication. I very much appreciate the help and support. I am glad there are knowledgeable people out there such as yourself to educate others and never forget the sacrifice of so many during WW2. People should never forget