A new student has figured out that this afterlife is bullshit. If he gets good grades, will he go to heaven? It's a farce!
His rant is cut short when he's confronted by the Student Council President...
Otonashi.
If you see it, then quit whining and seize the day, he says.
That's the show.
So, what's my takeaway?
First, despite what some people have said, this is not a comedy.
There are moments of humor, but it's basically earnest the whole way through. (The OVAs are more comedic though.)