Yeah, so? The cultural festival happens at that time. If you're going by the anime, the anime took random filler stories from whatever volume - the cultural festival happens quite a ways far down the line in chronological terms. And wasn't Shamisen explained on Volume 2?>>11193178
No, of course not. Just read them through 1-9. I don't know how you got through 1-4 if you're this confused about it. Just read them in order, that's how they are meant to be read, and any things that suddenly appear will be explained afterwards.