Warning: contains minor spoilers for My Hero Academia: Team-Up Missions volume 2!
The huge cast of characters in My Hero Academia means that sometimes, certain characters will fall out of focus for a while, as was the case for the villainous Himiko Toga until chapter 341. The second volume of My Hero Academia's spin-off My Hero Academia: Team-Up Missions was just released in English,, and with some of these characters coming back around, it seems that a few fan favorite heroes from U.A.'s rival school Shiketsu may be returning to relevance.
While My Hero Academia primarily follows the students of U.A.'s class 1-A, some academic events have put them up against students from other schools, who are just as eager and well-trained. Of the other schools in the series, the most prominent are Shiketsu High, located on the opposite side of Japan, and Ketsubutsu Academy, where Aizawa's friend Ms. Joke teaches. While some of the Ketsubutsu students (namely Yo Shindo and Tatami Nakagame) appeared briefly in chapters 307-309, putting their provisional hero licenses to use evacuating citizens, none of the Shiketsu students have been seen since 246, almost 100 chapters ago.
However, just because they haven't shown up doesn't mean they're no longer relevant. Back in chapter 323, when Deku is brought home to U.A., it's established that the fortified U.A., now acting as an evacuation shelter for refugees of the Paranormal Liberation War, is linked to Shiketsu. The exact nature of the connection isn't completely established, and the massive distance between the two schools is noted, but Principal Nezu assures the students that in the event of an attack, the entire school and everyone within can be moved to a secondary location like Shiketsu if needed. Presumably, the reverse is also true, offering a way to bring these characters back rapidly should the need arise. 323 also goes out of its way to show images of Camie, Inasa, and Seiji, just to remind readers that these hero students are out there somewhere fighting, too.
In recent chapters of the manga, the story has taken a moment to breathe as the heroes plot their next move. With only a week to spare, whatever plan of attack they end up going with is likely to be their last chance to stop All For One. It's already clear that every chess piece at the heroes' disposal will be put to use, including some ethically questionable options like using Aoyama and Midoriya as bait. To give themselves the best chance to win, it'd be foolish not to deploy the Shiketsu students in some capacity, although that doesn't necessarily mean fighting side-by-side with their U.A. counterparts. As several chapters of My Hero Academia: Team-Up Missions confirm characters from other schools haven't been forgotten, this seems even more likely
Establishing the connection to Shiketsu and reminding readers about these characters with fun team-up stories are good ways to set up their return. Now that the story is checking back up on characters that haven't been seen in a while, odds are good that the Shiketsu students will show up sooner or later, and their reappearance before the My Hero Academia story ends this year is almost guaranteed.