During the short time Yun doesn’t have genei jin, Yang has a far superior ground game. A yun that spams divekicks can either 1) be easily parried into launch into whatever or if you’re scared or not confident on parrying, then 2) jump back fierce the divekick once it gets close enough to you.
Jump back fierce sort of defeats the purpose of trapping Yun, because 1) you’re allowing him to build more bar and 2) you have to make up the distance while he’s building the bar. However, if his back is in the corner, then jump back fierce isn’t a bad idea because he’s being sent back there.
Whenever he gets genei jin, you always have the option of running away [if you’re not in the corner already with the twin’s far backdash, and sometimes you can get away with a backdash or two, then teleporting. However, teleport is a really shitty move, and more often than not you’ll get pulled into genei jin anyways.
At the range that only his shoulders and f+fierce will reach, that’s the spot where you’re kind of fucked, too. Yang has no real far reaching poke [at that distance] other than a slash, and it’s not difficult to parry it from that distance, not to mention if the guy is just fishing for it the whole time. Your best bet is to just walk into Yun, and scare him into getting airborne. A predictable jump or divekick is what kills the twins. Get in his head, get him scared and most likely the vast majority of players you’ll run into will jump.
In the corner, seiei enbu can be a source of massive damage against Yun. Knock him down and activate and even the standard slash combo will do at least 40%. Reset it and it does more. If you reset it with a command grab at the end, you’ve gotten 40% of your meter back, which is another ex slash. However, you risk too much in doing it, because 1) getting hit with 123 by yun is a lot of your life and 2) it’s seiei enbu. And you’re Yang. You’re the fastest meter builder in the entire game, and so you shouldn’t be overly concerned with building up another seiei enbu [unless it’s really close, and if it’s that close you wouldn’t take undue risks like walking in for a command grab anyway].
Something interesting I found - seiei enbu is the shortest bar in the entire game, but it lasts longer than genei jin by like a second or so.
I personally burn my ex when I’ve got a guaranteed change of landing it. Saving it in that situation is a bad idea, but using it randomly is even worse.
I personally like the SA3 for this match. I recently used SA2 against someone in a team tourney and I missed the knockdown into activation into yun can’t do much that seiei enbu gives. I also lost that match [damn].
Far away activations are near pointless against a far away Yang. Either activate SA3 or dash back activate, and start throwing out c.fierce. Yun’s toward+fierce can beat c.fierce clean, but cleanly loses to standing far forward [to my knowledge, I’m the only one that mixes it up], and so throwing those two moves out at certain periods means that Yun has completely wasted his genei jin - a lot of the time you’re simply trade a c.fierce hit for his divekick hit.
Even without EX slashes, Yang’s regular low forward xx slashes does noticeable damage to Yun, since Yun is juuuusssttt like Yang and takes damage like a bitch. A side effect of using regular slashes is that there’s more opportunity for that randomass slash crossup to occur. Great.
Also, if you’re going to use SA3, you might as well learn how to red parry 123. The only thing you can’t stop [and every smart player will try to do this] is either launch xx genei jin, or low forward xx genei jin. No character can do shit to that, but at least you can shut down his far away activation [sort of like chun li, but less risky if you’re slow].