All you need is two things to get interested into this. The fact that Kanon and Air character's are in this, and that the combat system is better than Marvel vs Capcom, but similar to Street Fighter Alpha 3, in a way.
Gameplay - Here's where the game shines. So what makes Eternal Fighter Zero different from things like Street Fighter? The first thing that's different is that there's a "charge" bar for each character. This bar will go up automatically, and it will turn red once it reaches it's limit. Usually this will go by in a span of 10-15 seconds of not being knocked down. Then if you don't do anything for another 10-20 seconds, the red bar will turn a flashing blue color. Basically what this bar does, is make it so all your special attacks are "charged", basically. If you have a red bar and use a special attack, the bar will be regular blue again. When it's flashing blue, you can use around 4-5 charged attacks before the bar turns normal again.
Of course, this doesn't mean that regular special attacks without the charge bar isn't useful. It's just more useful if it's charged. Also, if you're doing a combo or juggling, you can use a charge bar up to give yourself an extra half a second time freeze, which opens up more combo options or a finisher. I don't normally use this, but it has a lot of potential in the hands of a skilled opponent.
Then there's the combo system. It's sort of similar to Marvel vs Capcom, where you can start with weak punches and chain them into medium and then heavy attacks, finished by a special attack of some sort. The thing that's different though, is that it's more flexible. I can't really explain it, but the game is slower paced than Marvel vs Capcom is, but it's really not at the same time. Also, if you knock your opponent into the wall, they'll do a flying 180 arc back down, which allows you to combo them some more while they're vurnable. Of course, they can still break out of air stun, like in SFA3.
The whole ultimate bar works similar to Street Fighter Alpha 3, except you start out with an empty bar. Do damage and the bar goes up. Then once you reach level 1,2, or 3, you can pull an ultimate of some sort. If you've ever played Hyper-dimension, there's also a "Desperation" type move that requires level 3, that you can only do when your life bar is flashing.
Blocking is also similar to Street Fighter Alpha 3, except there's one thing different. If you tap the block button at around the same time you get hit, you'll get one of those half a second time freeze deals, where you can counter as you like. This takes priority over most things, and can be deadly when used right.
There's more to this, but you can see for yourself if you ever try playing the game.
Characters - Kanon and Air mixed together, with some other characters from Moon = Woohoo! The most noticible characters are probably Ayu and Misuzu, if you've ever watched Kanon or Air. All the characters pretty much live up to the anime version of themselves. Ayu still has her Taiyaki, and Misuzu has her dinosaurs and Yukito. It's pretty funny to see some of the moves they do. Other characters include Nayuki, Makoto, Kano, Minagi, and more. There's around 18-20 characters, I believe.
Sound - As with most fighting games, the sound is a very minor part of the game. The only thing I should note, is that Misuzu's winning theme and stage BGM are very similar to the Air OP, which is an extra plus. Other than that, nothing really special. Unlike Melty Blood, there is no vocals in this game.
Conclusion - If you're a Kanon or Air fan, you should probably check this out sometime. Of course, you'll probably want a controller of some sort first, before deciding to get this. Keyboard is definitly bad, but if you're not a serious gamer, then you might live with it. There you have it, Eternal Fighter Zero!