Harder Than Steel

Fourteen-year-old Izuku Midoriya has always been different-even among heroes. As Eijiro Kirishima's little brother, everyone expected him to follow in his older brother's footsteps. Nobody expected Izuku to skip several grades because of his intelligence and end up as a second-year student at U.A. alongside Eijiro and their friends.
Izuku's Quirk, Hardening, sounds familiar at first. But unlike Eijiro's Quirk, Izuku can harden his entire body and virtually any object he touches without a known limit. His version is considerably stronger than his brother's, making him one of the most unusual students in U.A.
Unfortunately, being ridiculously intelligent doesn't mean Izuku is immune to chaos.
The second-year group has become a disaster of friendships, rivalries, crushes, family drama, ridiculous group chats, and teachers desperately trying to maintain order. Bakugo and Izuku have an obvious rivalry that everyone else insists is something more. Sero and Kirishima are constantly causing trouble together. Mina is determined to embarrass Kirishima at every opportunity. Shinso has two dads-Aizawa and Present Mic-and has absolutely no idea how he ended up with them.
Meanwhile, the former villains have been given a second chance. Toga, Shigaraki, and Dabi are no longer villains, and they're trying to figure out what their lives look like now. Dabi is 18 and somehow ended up dating Hawks, who is also 18. Toga is 17 and has become close with Ochaco, while Shigaraki is slowly learning how to exist around people without destroying everything.
And then there's the Big Three.
Mirio, Nejire, and Tamaki have been aged down to second years, placing them in the same generation as Izuku, Bakugo, and Shoto. The three are still considered U.A.'s rising stars-but now they have an entire new generation of students competing with them.
Everything is mostly normal.
Until someone creates the group chat.
And then everything goes straight to hell.