I've read this one :) It's called A Belly Full of Fire by FruitPastilles.
I was able to find it because this was such a unique fanfic that I remembered part of the summary, "he breathed fire". Here's the summary:
When people asked Hisashi what his Quirk was, he'd flash a grin and say he breathed fire. It was a small lie, easier to say than 'my ...
Yes! More Like ENDEVIL, Amiright? by TheBabbleRabble (on AO3)
Kirishima puts his pencil down, turns to face Todoroki, and says as casual as a spring afternoon, “Bro, I really want to punch your dad.”
Or: Four times Todoroki’s classmates ruin Endeavor’s life and career, and one time they don’t have to do anything.
...Yaoyorozu's bit is in Chapter Two. And ...
Despite the sparseness of the question and details, I actually believe I read this a few weeks ago. I've read many BNHA fanfictions and hadn't actually seen this strategy before, which is why it stuck out to me when I read it.
The Fanfic Is:
Live a Hero by BeyondTheClouds777
Here are some excerpts from Chapter 11:
A robot spins around the corner, and ...