You should expect to have fun. Went last year for the first time (cause I had just moved to Oregon), and it takes a bit to get...acclimated. Not in a bad way though. Its just a bit overwhelming seeing so many people "from" so many different animes that you like. Also expect to spend a bit of time waiting in line. Now it's not to terribly annoying to have to wait in line, because you meet all kinds of people while you do. Make sure you come expecting noise. If you're the type of person who gets headaches easily, then bring something for it. I find it the most fun if you just let the con happen, don't try and plan too much it ruins it a bit.
I love these comments about meeting people and letting the con happen.
They remind me of one of my favorite sayings - at a con like Kumori, almost everyone you meet is just a conversation away from being a lifelong friend. Corny, but true.
That might be one of the most important things to keep in mind. In the outside world, anime is "weird Japanese cartoons for kids", and your favorite meme about Ed and Winry will just get you weird looks. At Kumori, that's something that most of the people around you have been dealing with themselves, and they not only understand what you mean about Ed and Winry, they have some interesting points about Al and Xiao Mei to boot.
Last but not least: It's quite true that you should expect noise. But as staff, we will be cracking down on extreme cases this year - you'll still have to deal with people screaming embarrassingly-outdated memes about "the game", but you won't have to deal with anything loud enough to cause pain. Or if you do, expect the person who causes it to find out in no uncertain terms that they will NOT be doing so again. (See your bag stuffers at the con for more details.)