We live a walkable distance from a Jieitai (自衛隊) Base, or a Japanese Self Defense Force Army base. Jieitai has a navy and air force as well. I think a lot of foreigners don't realize this exists in Japan. (I only found out about it in the US when I could meet some visiting members of the Japanese Navy while volunteering at a Japanese school.)
The base in our city is a good size with a school, several dormitories and other buildings, and a big open space. They have their own little walking track inside the premises. Civilians are generally not allowed to enter the space.
Last month we were allowed to enter for the special Hanabi Taikai the Jieitai puts on every August. There were lots of yatai and information tables, performances by a local hula dancing club, and of course fireworks. We were able to watch fireworks very close to where they were set off and it seemed liked they exploded directly above us. This was a better experience than the more popular Hanabi Taikai in town, as it was closer and not as crowded.
This month, there was an open house event at the base to allow civilians to come in and see demonstrations and exhibits of the military equipment they use. I heard this happens at least once a year. We arrived while the demonstration was in process. It wasn't very crowded, but families were standing and even sitting on mats near the large roped off demonstration area. Most of the visitors seemed to be family members of the staff.
We got to watch the servicemen demonstrate throwing grenades, shooting machine guns, and shooting huge cannon guns called kahou. They drove around in various tanks and helicopters flew overhead. There was a demonstration of a war scenario, where each side shot at each other and threw grenades (all blanks, I'm sure), then one side advanced and the other waved their little white flags to surrender. When the cannons were fired, signs were held up and an announcement was made to be careful as there would be a loud noise. It was surprisingly loud and ground shaking. (I think I had heard them practicing a day or two earlier and was a little concerned at hearing gun shots. They usually give advance notice in the neighborhood announcements if there will be shots fired at Jieitai.)
We were also allowed to enter some of the buildings, including the store selling military goods and souvenirs. There were a surprising number of US military items there. Next to that there was a convenience store for the Jieitai staff, quite similar to a normal convenience store. Some yatai sold food or toy guns and there were a few tables for kids to get snacks and try shooting toy guns.
Outside we could see several types of military vehicles the army uses as well as the different hand held weapons. All the tanks have a white sakura emblem painted somewhere, sort of a delicate touch to such heavy machinery.
Military demonstrations aren't something I'm especially interested in, but I like field trips and it's still very exciting to have the chance. Your area might have a Jieitai or a US military base as well. There are some cultural events put on by both groups – I heard Sasebo's US Naval base has a Fourth of July (US Independence Day) event open to the public. It's worth looking into what's offered in your area.