So, May. May is a real annoying piece of work for many reasons,
and I wanted to bring something up that causes alot of people issues.

Totsugeki, or Mr. Dolphin is a big part of May's pressure. Defending
against this move properly is critical to preventing her from just
running game and snatching momentum. The situation that happens after
blocking Dolphin, S in specific, is the most important interaction in
the matchup.

So, the first thing to understand is that you cannot merely react to every
situation that happens after blocking S dolphin. You must commit to an option,
immediately. Indecisiveness is your doom. What you want to do is choose a
strong option and then react to the situation that comes after the next
interaction. If you try and counterplay everything May can do when she's
going, you're just going to get overwhelmed, get counterhit, and lose.

Keep in mind, what I'm going to explain is simply an introduction to the
layers of interaction with fighting May. There's much more you can do to
option select her pressure, and defense against her is still developing.
So, what are our options after blocking S dolphin?

The first one, and the one I use most is 2S on block, immediately.
A few reasons why this is good:.
2S is very likely to crush almost any option May does
that isn't defensive after she makes you block S dolphin. That means
S dolphin into a button, S dolphin into another S dolphin, S dolphin into
backdash into another S dolphin can be blocked after 2S, S dolphin into jump
lets you recover from your 2S...

It's a strong, mindless option on the part of Nagoriyuki that lets you
use your brain on other things, as discussed earlier. The reason why this
works is because May dolphin is -5 on block, and 2S is disjointed enough to
where May can't fight back against it in most situations. You can pretty safely
crutch on it, and just wait for the layers of interaction that come after.
Either she evades it, or she does something and gets counterhit by 2S. Take
comfort in this.

Now, if may is way closer to you, I'd recommend you change out using 2S
with 2K or 5K, as May might manage to hit you with another dolphin before
2S starts up, or use some sort of light to stuff you. 2K also stuffs repeated
S dolphins while having a faster startup, protecting you up close.

The second option is to simply block. It's pretty difficult for May to
actually open you up after a blocked S dolphin. Like, she has to run all the
way up, knowing that shes super negative, and try and grab you or create more
pressure, it's not likely to work if you stay sharp. She may present an
opportunity to get outplayed by doing something overaggressive if you're
patient.

The third option I'd recommend is doing spin, or slide, or 214H. Oftentimes,
May wishes to abuse the backdash button to goad your counterattack then
pressure with an immediate dolphin. If you're down to call this tactic out,
then slide will hit her right out of backdash, giving you a massive combo,
and all the momentum. If you're feeling very brave and disrespectful, you can
also just do a 5S as well - If May backdashes and does something that isn't blocking
or jumping, you're sure to hit her and get something started. 5S is very slow,
however.

Again, the key is that you need to use these options decisively and mindlessly
so you can use your mental resources in other way. It'll be pretty hard for
May to force her offense if you automatically do what stuffs her dolphin pressure,
also address her IADing at you afterwards, or trying to command grab, or 3K,
a bunch of stuff. Implement this, crutch on it, and life will be alot easier.