What's with all the weird writing/symbols in the hot springs in 3rei? In episode 5 of Prisma Illya 3rei, we find that Gil has somehow pulled an entire hot springs out of the Gate of Babylon. The walls surrounding it have banners with a number of strange symbols and quintessentially-Japanese words on them. 

You can see the symbols for yourself below; some of them are very strange, like the biohazard symbol (☣), the radiation symbol (☢), and a pair of clubs (♣) attached end-to-end. The words are "bonsai", "Mt. Fuji" (fuji-san), "sushi", "bushido", "matsuri", "kami", "sumo", "squid" (ika), "tenshukaku", and "heat haze" (kagerou), plus one on the far-right in picture #1 that is cut off. 

I have to imagine there is some sort of joke here I'm not getting. What is it?


   
 
 
 
 


(The images are spoilered because naked-but-steam-concealed characters.)
The banner looks similar to 武者幟 (warrior flag)

Around AD1600, There are civil war in Japan.
In that time every warrior show that flag to recognize each other.

Wikipedia have some picture of that war.


Or some city selling that flag as goods.


These flags have name of the 将軍 (General) or 紋(the mark of the family).

In that ilier's case, it uses same format, but it doesn't use actual mark or name.
I think it shows "Gil's wrong Japanese stereotype".