Been playing a lot vs. two decent Yun players. St. MP is really really good in this matchup, it can beat out lunge punch, divekick startup, and sometimes it will hit divekicks in the air. The only issue is that it is quite finicky and range dependent on whether you’ll end up with a trade, beating cleanly, or getting beaten cleanly. It’s not really something you can do on reaction, but it beats out a lot of Yun’s options that seem to “let him in on you for free” if you throw it out as a prediction. Obviously you can cancel it into a lot of stuff if it hits, and be ready to hit confirm into super should you have the meter.
Today I tried playing a super turtle style against Yun. Basically I dedicated my meter to EX SBK on reaction against divekicks. It’s the only thing Chun can do to reaction anti-air a divekick, and given Yun’s low HP it’s well worth transferring your meter into damage and discouraging divekicks. Yes it’s nice if you can save up for super, but in this matchup I feel that it’s not worth it to save meter when you could be using it to punish divekicks. The main time you want to go for this is when he gets at that mid range distance where he can do a really low divekick that you normally would just block and can’t AA with any normal; these are the divekicks you want to hit with EX SBK on reaction. As soon as you hit with an EX SBK you can throw out a fireball, build meter by whiffing some legs, and try to make back as much meter as you can. I found that when I played like this, it was actually very frustrating for Yun players to get in on me. I tried to turtle and EX SBK all the mid range divekicks, and I also neutral jumped a lot when at full screen and 3/4 screen looking for lunge punch punishes. Most Yun players will try to reaction lunge your fireballs, I have been trying to only throw fireballs at safe range and then fake like I’m going to fireball at his lunge range, then neutral jump to try to bait it.
If you just kind of alternate between these two styles of turtling and waiting for him to get in on you, it’s pretty hard for him to get in without a lucky guess or doing something risky. At times you’ll want to forego turtling and just rush him down really hard after a knockdown, but I tend to prefer very “soft pressure” that has little risk of getting me knocked down and having to deal with his divekick pressure after a knockdown and especially near the corner. Sometimes it is worth it to just go all in rushdown, but in this matchup the risk/reward is really off because while his DP doesn’t really hurt that bad on its own, allowing him to have divekick pressure off a knockdown is a massive disadvantage for Chun.
When he does manage to knock you down or otherwise is going for full on divekick pressure, the best thing I’ve found to do is rely on backdash or EX SBK when you think it might work. Even if he hits your backdash you’ll usually at least escape the pressure. Even if he baits the EX SBK, you were probably going to eat damage sooner or later if you just sat there blocking. There is some really annoying shit he can do when divekick pressuring you, but if he ever starts doing neutral jumps after a divekick (usually to bait an EX SBK) I’ve noticed you can just reaction U2 for a really free punish. Just remember that when he is in on you and divekicking, you fucked up and this is your punishment for fucking up. This is not a situation with an actual solution, I’m saying EX SBK and backdash but that’s more like the only possible thing you can do; it’s still not a good solution. If he is in on you and divekicking, this is what is going to lose you the round.
When he is building meter with palm, you can walk up behind a fireball and standing fierce him from a really good range. If he is doing the palm spam it’s usually to force you into him and its a sign that he is getting frustrated by your zoning. I like to try to act like I’m getting impatient and walk in behind fireballs but then neutral jump and look for a punish on a lunge or a divekick.
I’ve also been throwing out some EX fireballs when I’m just outside of my sweep range. It generally will punish him from walking forward when he thinks he’s out of range of all your moves. If he happens to do a non EX lunge, any poke, a low whiffed divekick, or a focus attack (this is the main thing you’re looking to punish with EX fireball at this range) you can hit him with it.
Mostly I’m just trying to get any hits in where I can with stuff like reaction EX SBK anti airs, EX fireballs, standing far MP catching stuff, and then once I have a significant life lead I just look for the “big mistake” of a random full screen lunge, blocked DP, etc. etc.