The Chun match-up hasn’t changed at all since Vanilla really, minus the fact that Chun can now combo into Ultra 2. I wrote something on the match-up quite some time ago, but I think now it deserves a reboot:
— Focus punishing a move can already lead to cl.MP xx HK CW, and there won’t many any other opportunities to use Ultra 1 for the most part. U2 stops meaty cross-up flips and jump-ins from being a major problem by turning them into damage opportunities. If you get into range for Flame Kick FADC against your opponent often, you may consider using U1, but I’m inclined to think its not worth it since Chun’s offense can be scary.
— Chun is ineffective here. She can throw FBs all day and you can absorb, dodge, or block them all day. Absorbing them will put you in a strong defensive position since you’ll build U2 early on (a solid tactic). This stops her offense from being a threat during the match so you can focus on playing footsies and absorbing her long pokes. Forget about throwing EX CW from this range, and just close in by walking once you feel that you’re ready (or let the Chun player close in when she’s tired).
At this range, Chun will consider throwing FBs and dashing in to knock you hit you with Hazanshu, st.MP, or a cr.HK. Absorb the fireball at the appropriate range and backdash so you can whiff punish, or block the incoming attacks so you don’t lose positioning. If Chun looks like she’s already caught up to the FB (by using FADC or just by dashing up a lot), don’t think about Focusing it. She’s already free to hit you by that point so just block it or dodge.
— This is where Chun can be more annoying since her st.HK has such long reach and is tough to focus because of the angle that it comes in. Chun is also prone to step in to do cr.HK and st.MP from time to time or dash in and throw. Focus is generally a strong response to her pokes, but you have to recognize when she does st.MP as it can be canceled into a move that will break your Armor. Have a sharp eye about whether you can land Lv2 or not; if you only get Lv1, it may not be worth dashing in unless you’re willing to take a chance on a point-blank CW/Flame Kick. Her up-close mix-ups can lead to a lot of damage, especially if you get caught late teching with a Hazanshu.
cr.HP is great here for punishing st.HK whiffs since it goes right under and hits Chun where she’s vulnerable. It’ll also keep Chun in check for when she tries to dash forward or come into position for cr.HK/st.MP. This range is where you’ll find the opportunity to push Chun to the wall. If you can’t get her to slip up defensively, approach cautiously to just about where her cr.MK/st.MP works. With strong reactions you should be able to stop her from dashing in to throw or do a Hazanshu. Keep blocking until that time comes. A random MK CW at this range would also be difficult to react to, but choose your spots or you’ll be batted out of the air (for a little damage).
Those are the two ranges you want to be defensively. Once you get Chun into the corner, the mid range point also becomes a strong offensive position since Chun can’t jump at you or throw slow pokes. The only time you want to think about getting close is on a knock down when Chun has no meter to defend herself; as a defensive position, close range is horrible for Fei since Chun’s normals give great frame advantage and can be used to tick throw really effectively there.
Your mind should be set on the far wall. That’s your only goal for the first 20 seconds of the match: “How do I get Chun there?”. The answer is usually patient walking. Often, Chun will backdash/walk her way into the wall since her mid-range spacing is important to her, as well as her FB charge. Many Chuns also foolishly think that staying at long range is important and will backdash much sooner than they should. Once you’re ready to go on the offensive, sometimes the best offensive action is to just walk forward to mess with her spacing.
Patience is definitely key as with all fights, but spacing is even more important here. Until you’re at that mid-range point you should be care free. At mid-range just keep in mind that you’re looking for something to punish rather than for something to defend against and base your spacing on that. Keep at least one EX meter stocked for that range and you’ll definitely find something.