Sent back to isakai world?
So this may sound odd, but this is from my dream which seems familiar as I've either watched this anime or seen it in a reel or something.
So from what i remember mc and fl and maybe some of their friends are sent back to what seems like their last day in their isakai? World. When they appear people are surpised because space/time shouldn't be fragmenting anymore after a big battle that just happened. Not sure if they came from real world or isakai world after a reset. The mc is OP, but moreso in cunning and sidestepping than humongous feats of power. The world is slowly disappearing and there are people trying to fight them at first, then by the end everyone is just trying to survive. Mc isn't too worried about the world disappearing because he knows this isn't the end, but the beginning.