Unmentioned anywhere since I could not fit it in, Shouto also actually reincarnated on Gaia; he's Genesis. For those familiar with Genesis you know why this is funny in a fucked up way. Cloudsuki is not aware of it, though Sephiku is (and is simply beyond the point of caring).
Only Cloud, Sephiroth, Zack, Aerith, and Genesis are reincarnations of BNHA characters. Everyone else has a soul native to Gaia
Sephiroth accidentally regained his memories of being Izuku post-Advent Day. He literally fixated so had on Cloud he remembered who they'd used to be (and since being in the Lifestream at the time was able to realize who Zack, Aerith, and Genesis had been). This was added by Katsuki and Izuku's well, own and much healthier, mutual obsession.
For those wondering at the end, the implication you should be taking is that Sephiroth is about to cause the Remake continuity
For those who follow the anime rather than the manga, fairly early on in the ongoing War Arc Katsuki nearly died due to a heart injury and survived due to plot armor and open jeart surgery. Here he didn't get so lucky a second time.