Great idea! After all even if there's a vast majority of Japanese people around there are many who are from other places and even from worlds that have no Japan at all. A just Japanese festival would have little meaning if others can't enjoy it to its fullest.

At worst case we can just make a generic summer festival. I'll also see what things can be done at the festival to make it enjoyable! Fireworks are a must, obviously, and catch-the-fish games!