This guide is written on the premise that Celty is the assist used so please take caution.
With Asuna, your goal is to get your initial hit and then go on the offensive with Celty 6S Oki. When you’re in neutral you want to use Asuna’s great normals to contest the opponent and make them respect your space while invading their own. For example, you basically want to hit them and do something this
Example: 5A 5B 5C 5AB 236AB 66 6S for Oki
I will detail your oki options later below as well as other means to put yourself in this situation to accelerate Asuna’s gameplan. Asuna’s comes on the ground and in the air can all lead back to the Celty Oki gameplan and so your goal is to keep the opponent in this blender and ultimately kill them from setplay.
On offense you want to utilize Asuna's mobility to cover space and her amazing normals for space control as well as keeping them cautious on the control with Celty 5S. Up close you can stagger pressure on them with 5A and 2A, you can do block strings like:
2A 5A (2A or 4AB)
2AAA 2C (214[A] if blocked, 5AB if it hits into your desired ender)
The most important part about your blockstrings is that you don’t want to just mash it out but mix in some delay to apply stagger pressure and keep your opponent second guessing on when they can mash out.
Jumping in and throwing out jC can go a long way as well, however, be careful not to get anti aired. Try to space it out so that jC will make contact with your opponent by the tip rather than doing too deep in with jC otherwise you’ll do yourself more harm than good.
If you notice your opponent going for a lot of air approaches to avoid Celty 5S you can also meet them in the air with Asunas jA and jB to keep the momentum in your favor.
If you have the life lead and you want to play a little defensively you can easily create a wall for your opponent simply by upbacking and pressing jC, due to jCs amazing range they have to take risks to get to you and that’s where you attempt to call them out.
Characters with fast projectiles can call this out such as Shana 236AB or Tatsuyas 236AB however other characters with no such option have to work. Characters like them will try to approach from the air as you're landing, similar to on offense you can quickly meet them in the air with Asunas fast and strong jA or jB (depending on their height) or wait patiently on the ground and answer with her 2B.
After you go into trump, whether you combo into it or access trump using it as a reversal option, Asuna’s pressure offensive and defensive options enhance greatly even though she lacks an install trump. On offense you have the ability to assist cancel for free, call your assist at anytime in neutral and reverse beat your normals. With this in mind here are some tactics you should incorporate into your play once you are in Trump.
Because of how fast Celty 5S is, under trump you can super jump forward and call Celty 5S while their eyes are on you. Celty will act as a “hidden projectile” to them and on hit will give you HKD. This is especially strong in low health situations and gives you a lot of field control. You could technically use 6S as well however it would be more advised if you’re trying to keep your opponent locked down longer with its delayed entry and 2 hit assist.
After hard knockdowns, you can use the newly acquired jump cancel property to cancel your OTG attacks into a safe jump setup while calling 6S at the same time. An example of an OTG string includes 2C > 2B > 2A > 5C > 2AA > 6S. Off high proration combos 2AAA > 5B > 6S is advisable.
On your jump ins you can reverse beat your jB into jA for a double overhead, under trump if you are super jumping on your opponent you can keep them blocking with the tactic above with 5S and while they’re blocking you can attempt to open then up with jB jA land and go low with 2A or go with 4AB for a triple overhead attempt.
With the trump benefit of being able to jump cancel all of your normals or reverse beat them. With this in mind you can use it to utilize Asuna's 5C more to try and snipe with 5C pokes and if it’s blocked you can reverse beat to 5A or just jump. Keep in mind it’s still unsafe on whiff.
One of the few assists that enables Asuna to have left/right mixup, it can be done in a variety of situations. From both EX enders, 236AB/j236AB hit > slight delay > 6S call > super jump over opponent then either jump back to the side you started on for the fake cross up, or neutral double jump to remain on the other side as close to the opponent as possible to make it ambiguous as to which side you are on (note that you shouldn’t be crossing back to the side you started on) and go for standard jump in mixup (jump in/empty jump low/throw)
With the trump benefit of being able to jump cancel all of your normals or reverse beat them. With this in mind you can use it to utilize Asuna's 5C more to try and snipe with 5C pokes and if it’s blocked you can reverse beat to 5A or just jump. Keep in mind it’s still unsafe on whiff.
While you are on defense you can mash on 1/3s to call Celty’s 6S assist out, she comes from above so she can’t be hit out of her animation. Against players who aren’t aware of that, she can catch them off caught during their pressure string and not only stop their pressure but give you a free combo and allow you to take your own turn. However as the startup is fairly long, you still need to block the opponent until she appears as getting hit during 6S startup will cause her to disappear.