It was here. The end of the War happened. And nobody won. All For One died, and with him as did most of the League. But the Heroes also didn't win. Shigraki had managed to touch the ground, using his increased Quirk to his advantage, devasting the entire country. Heroes, villains and civilians alike were caught in the attack.
It was hard to believe. But it was true. Now Katsuki Bakugou wonders the ruined wasteland of Japan, wondering what to do now. Seeing the devastation, seeing the results inflicted onto people. It was a Total Failure. He doesn’t even fully remember what happened, having hit his head at some point as buildings started coming down.
So he tries to not think about. He won't think about how he failed Izuku, has no clue whether he is even alive. He won't think about his parents. He won't think about his classmates. The best thing he can do is try to help protect people. So he wonders around, like a zombie, his hero suit bloody and torn.
You find him. A survivor. The only person besides some crazed villian or the loose Nomu around. "What are you doing?...You...You need to get to safety..."