Good Afternoon Leo,
I am by no means an "expert"....I can't speak to the authenticity of the flag and I know enough to get myself in trouble. There are guy like Dr, Mike Bortner who has written the book on these flags that are far better then I'll ever be. What I can point out is the flag appears to be "home made" as opposed to a production type which is what they (the Japanese) did. The tiger is cool....artwork flags especially with tigers are highly sought after and make a "yoshigaki hinomaru" flag more desirable and are a little more hard to find. The written line far upper right above the tiger is "Ki bun cho kyu" or "everlasting good fortunes in war". This is a common saying found on 90 % of these flags. It is also seen again in picture 3 written vertically large kanji center of picture. Looks a little different likely due to the hand writing. I see many names but what is of interest is on the the vertical line of kanji on the far left....the top word is "kai gun" which is thew Japanese word for "navy". A little more unusual. I think there are other guys on the forum that can help with a better translation. Thanks for posting and good luck with this flag !
Tiger Thankyou for the information given to me,
The flag came back with a marine, his dog tags and his medals.
This came direct from the family so thats the only history I have, but like yourself I really like this flag.
Looking forward to other members opinions, and I thankyou for the details you have given thus far
That navy connection could be quite an amazing find !