I am very lost, can someone help?

So I've watched the entire series and am currently about to watch the last episode of Owari S2. The thing is, it's been a while since I've seen the series, and frankly, I've been very lost this season.. as in I really don't have any idea what's going on.

Could someone, like, explain the current story of Owari S2 with the needed background information? I really don't know why but I'm forgetting so much.