Official Quirk Explanation (This is important to understanding what's going to happen when she fights in the final round)
Because a lot of people are still a tad confused (I don't blame you it's not a very straightforward kind of quirk) I'm going to try and explain Y/n's quirk, the best I can and please don't hesitate to ask questions, I read every single comment so--
Y/N has a third nervous system. The human body originally has two- central and periphery. One is the brain and spinal cord (central) and the other is the nerves that branch off. Y/N's third nervous system is an extension of those nerves that work by sensing things outside her body. For example, when it rains, you can feel the raindrops when they fall on your skin. Y/n can feel the increase in specific elements (water / H2O) before the drops even touch her body. That's her quirks first ability: sensing elemental states and quantities at the atomic level. Second, after she senses these conditions, she can alter them. Rain is just two hydrogen atoms and an oxygen atom interacting. If she wanted to, Y/N could use her quirk to pull apart the two hydrogens and oxygen by willing it. That's her quirk's second ability: manipulating atomic bonds.
As for limitations: Y/n can't create or destroy any elements, that's actually impossible (even though most quirks are lol). So she can't just create oxygen when she needs it. She can, however, displace oxygen, meaning manipulate pressure so that the oxygen floats upward or downward, making the exchange of oxygen between her cells more efficient (that's why she doesn't run out of breath, her body does this on its own).
Important facts:
The reason her ears ring is because of the frequency. When atomic bonds are broken it releases energy. Since Y/N does all she can to suppress her quirk, she's containing that energy which builds up like pressure. It causes tinnitus. This is also symbolic of her denial. She doesn't want her quirk to exist, therefore she chooses to not hear it, which causes her pain.
Nervous systems function, for the most part, involuntarily-- meaning you can't control the actions of those systems by will like you'd move your hand. Y/n's quirk is similar. If she is in physical distress, her third nervous system works the same way any cell does. It'll protect the body without her choosing.
***
No one truly understands the size of a person till they have to carry one.
But you did. Every bone, every ounce of blood, you could hear and feel in others since you could remember. You knew the exact weight of every single one of those cells, not from experience, but rather from concept. Still, you weren't prepared for carrying a fourth of Bakugo's weight on your shoulders.
Probably because the weight of his expectations for you was even greater...
There wasn't an official announcement or anything of the sort.
A single swing of Midnight's whip, a ring of a bell, and suddenly it was a free for all.
Alright.
Thinking time.
10 teams. Only 4 make it out.
The majority of them weren't powerful enough to even consider going for your headbands.
However, Sero and Mina joined. And though with you and Kirishima standing at the front you made formidable allies, your leader was obnoxious enough to attract too much attention.
He wanted to go for Mydoriya.
Fair enough.
But you needed an opportunity.
And his team wasn't exactly defenseless.
Uruaka touched one of you and it was over.
Tokoyami's dark shadow was already leading as the front horse, blocking and deflecting any teams that went for their headbands.
Add a crafty little support course techie and they had all they needed.
