It looks very fake. My guess is that it is a Chinese-made replica.
The flag should be rotated 90 to the left, so that the four large characters should be on top. The four large characters are 武運長久 (good luck in battle). The rest are names, but they are written in such as way as to be illegible. Indeed, a few look to be Chinese-inspired names. There are a couple of standard patriotic slogans on the flag and a date of Shōwa 19 (1944). The date looks as suspicious as the rest of the flag.