Konnichiwa Mikemike88-san!
The shrine's seal is in the upper right corner. This shrine is the most prestigious shrine in Suō Province. And beneath the seal, a waka poem that is works by Emperor is written by the chief priest. It also has the chief priest's signature.
Anyone who visits a shrine can obtain a shrine seal. However, I don't think it's easy to get on the chief priest's handwritten waka poems or autograph.
Because counterfeit goods are mass-produced, many of them have the same handwriting, and because they are written in haste, many of the letters are faded.
But there are no characters that can be immediately identified as being in the same handwriting on the flag. The signature is neatly written, and not a single letter that is faded.
Along with names, many messages are written. It's a shame that almost all of them are slogans, and some even contain inappropriate words like "玉砕", but I can tell that they were made with great effort.
Considering all of the above, I felt that this flag was made with great care.
NANGI