[Katsuki knows. He knows how hard it is for Izuku to accept that there might just be a possibility of losing Katsuki, and how hard it is to accept that he already almost did. It's not like Katsuki doesn't have nightmares about dying ever since that fight. It's something that's been on his mind...]

Then we'll make sure the world never loses Kacchan. I'm super hard to kill now, remember?

[They argued so much about it!]

And on top of that, you and I can be extra careful from here on out. I want to be smart, and win my battles perfectly. And I know I'll need help in order to do that.