On the right side (vertically) is the name of a school that presumably presented the flag: Fukuchiyama Shukutoku Kōtō Kasei Jogakuen - which in English would be something like Fukuchiyama Shukutoku Home Economics High School for Girls.
Across the top are the words 祈武運長久 ("pray for good luck in battle"), which is nearly ubiquitous in these flags. The rest are names of the well-wishers, with one or two (or three) patriotic slogans on there. There is no one specific addressee, so maybe this was presented to a group of soldiers.
The school exists (and still exists today, albeit under a different name). I think it is authentic - but grading it on a scale of collectability, my personal opinion is that it is slightly less desirable than one that is addressed to an actual soldier. It just feels like this particular flag may have been one that was made in batches, and that possibly this is one that never got presented to a soldier.