Hello Carl,
It looks good to me. Writing on the far right is 祈軍旗下御奮闘 (Pray for (your) brave fighting under this battle flag).
Next to that in the large lettering is 祈武運長久 (Pray for (your) good luck in battle), which is the most typical phrase found on these flags. I guess 90% of them have this phrase.
Next to that (nearer the red disk) is 七生報国 (a patriotic phrase meaning basically "give your all for your country"). Under that looks like a name 友廣八蔵 Tomohiro Hachizō. Slightly odd for a name to be written this prominently unless it were the recipient's name, but if it were the recipient's name you would expect an honorific to be attached to the end.
There on the left there is 尽忠報国 ("unswerving loyalty to country"), 必勝 ("certain victory"), then on the lower left is 米英撃滅 ("destroy the Americans and British").
At the very top is the single character 断, which is like "determination!". It's something I've never seen, but its not so weird that it gives me any doubts. Just unique.
In one sense, it has so may typical phrases that it is almost suspiciously cliched. But the writing styles of the names is all different, and it doesn't look artificial (in my subjective opinion), so I'd say it appears to be authentic. I can't find an obvious recipient's name. There is the option of sending it to a Japanese embassy or to the
Obon Society, where they can research some of the names and see if they can identify an owner, but in that event you have to surrender the flag to them and there is no guarantee they can find the relatives of the owner, or connect you to him.