Shigaraki is just tired of always getting pushed around by Midoriya and the rest of UA, he decides to take revenge, he frames them causing them to be considered as criminals and they couldn't show there faces anywhere. Aizawa sent them to stay at salt city intill they clear there names. The students met Reigen and Mob and they let them stay at the hideout, the villains knew where they were going and wanted to silence them , they kidnapped reigen and twice cloned a creepy imposter of reigen who was a murderer. Later they discovered the villains are behind this all and didn't except this and so they fought back. - (Just a FYI the story will have some ships in it alright! ☝)