Here's how I fight Ara. And cut me some slack, I'm not as high-tier at giving out advice as Spark is.
Offense
Many times, starting out the match with a sj.C or IAD j.C will be sufficient as a lot of Arakunes think: "get away and set up curse traps". That doesn't mean you should start every match with one, just confirm that he starts jumping away and react accordingly to it. Don't let him set up his little obstacle course, keep on him.
If he does slip away, just wait for an opportunity to hit him while he's doing something. Deploying a cloud or j.D, for example. Even if he blocks your j.C it will still ground him, and give you an opportunity to do some ground pressure, and possibly get a hit confirm into a nice meaty combo.
Clouds are a pain in the ass, but they aren't something that should dominate your entire offensive strategy. If you see an opportunity to hit him, the pay-off will be worth the little bump to his curse meter. But that doesn't mean you should just absorb every cloud he puts out, that'll put in you some real trouble. Only take the cloud hit when you can afford it. Spark has some excellent advice to weave around and deal with clouds in the above post as well.
One thing to really watch out for is Ara's 5C. This thing has excellent invul frames and IIRC it's jump cancelable on block and the hit box is quite large. So IAD into a barrier block isn't the best answer for this situation as the offensive could be turned against you instantly. Try to land just shy of 5C's reach and begin pressure there.
Defense
Arakune's mix-up is pretty weak. 6A is his only really notable threat, and often times it follows a series of 2As. So if you see the low jabs, chances are a 6A is going to follow. j.B is a major pain in the ass, and he will use it to close gaps. It can be countered with a j./6/5D if you can get the weird timing down or a real quick Hotaru.
Something to watch out for is his 2D, which is very spammable and you should do your best not to block too many of those, because the curse he can get off of those builds up pretty quickly. Not much I can really say about this, just jump out of it and keep going.
Defense Under Curse
As long as you entered curse mode without being hit initially, you still have a chance to come out of this round mostly unscathed. There are few things to watch out for:
1. Teleport (spam) cross-ups: Some Arakunes will literally just spam teleport back and forth in an attempt to get you to block in the wrong direction. It's pretty easy to see coming, and shouldn't give you much trouble. Regardless, watch out for it.
2. Grabs: I'm not sure if getting hit by bees first makes all of Ara's grabs become purple/pink grabs, but I think it is. So grabbing won't be a huge concern, so long as your reaction time doesn't suck that bad.
3. Mix-ups: Like I said before, the thing to watch out for is 6A, which usually follows after a series of 2As. Occasionally, they'll confuse you a little and appear in front of you only to instantly do 6A. The only other mix-up on the ground I can think of is his 6C. And if you goes ahead with all three hits, well then you have a free pass to mess him up. Just use 6D on the third hit of his 6C and you can do some damage to him while in curse.
4. Projectile Barrier: If you do manage to make one, make sure to protect it. That's right, protect it. Do that and it will protect you in turn. Reason why, is because Arakune can easily disperse the barrier by jumping into it while blocking, so if you can keep him out, he'll likely spam bees, and if he doesn't, then go on the offensive. I've never really made good use out of this method though, it's a thought however.
After Curse wears off, it's just the same stuff as before. Keep pressure on, pick the right moment to go on offense and block block block if you get cursed again. Anyways, this is just my mindset when it comes to the match-up. I don't know how much it'll help against pros and such.
