I'm replying to myself here, just in case anyone in the future is looking for information about the Shingen-ko Festival. My teenage daughter and I made the trip out to Kofu for the Saturday afternoon and evening of the 2012 festival and it was a wonderful experience.
We took a direct train from Shinjuku at 2:00pm, which arrived at Kofu just before 3:30pm. As we exited the station we could see the "warriors" assembling in the square to our right, so we went over to get a closer look. Although this assembly is on the festival schedule, it's not a formal event and you're quite free to wander around and take photos of the costumed warriors. People were very happy to pose with us and we were also given free bowls of some kind of noodle soup. It was quite tasty. :)
Then suddenly the banners went up, the warriors let out their battle cries and the march began! We followed the parade through the streets to the castle ruins and then back onto the streets. There weren't all that many people around, and we soon found out why. As we headed towards one of the main cross streets we could hear music playing and when we got there we saw the entire long street filled with costumed dancers. The program said that there would be 1,000 dancers and this may well have been right. In all honesty, it didn't look like an especially traditional dance - more like a highly energetic aerobics class. :) But the dancers looked fantasic and everyone was clearly having a wonderful time.
We lost sight of the parade at this point, so we headed back past the station to get to the big square where the warriors were meeting up with "Takeda Shingen" and his generals (all on horseback). We soon found that this is where the rest of the town had gathered! It was very crowded and we really couldn't see very much.
Then the most extraordinary thing happened. The people in front of us looked around and saw my daughter, looking all squashed and a bit forlorn. They said something to the people in front of them, and before we knew it, people had cleared a path and were ushering us up to the front. It was such an unexpectedly kind gesture that I almost cried. And then people kept passing us food and sweets! People of Kofu, you are the nicest people in the world.
After the presentation of the warriors, the parade re-assembled and we followed the crowd back to the castle grounds. There seemed to be another ceremony or performance going on at a special stage, but we didn't squish our way in to see that. We wandered around the park, bought some food at some stalls and then watched the fireworks. After that, around 8:30pm, we made our way to the station and caught a train back to Shinjuku. There were no direct trains at that time of night, so it took a bit longer (with one change) - I think just over 2.5 hours. We made it back to our hotel around 11:00pm.
The Sunday program also looked really good, with swordsmen and drumming, but we couldn't do the trek out there again. Maybe another year, if we're lucky, we'll go and actually stay in Kofu for the entire weekend.
One tip: although it was lovely spring weather during the day, Kofu is in the mountains so when the sun went down, it got quite cold very quickly. We could have done with some warmer clothes for the evening; as it was, my daughter got to wear my jacket on top of her own and I got to shiver a bit! The things that parents do. :)
I hope this helps and that anyone going to the festival enjoys it as much as we did.
Edited: 2:42 am, January 01, 2013