At one point Nagisa and Tomoya get married and Nagisa getting knocked up soon follows. I would mourn the lack of fan service but really i found Nagisa to be the least attractive female character in the series.
Anyway, they naturally revisit the plot detail about Nagisa having very poor health, so some doubt is cast as to whether or not she would survive labor. Tomoya convinces Nagisa to go to a hospital instead of trying to give birth at home, but before the baby comes a blizzard arrives and the ambulance never shows up. Nagisa successfully delivers the baby but then croaks.
Then, as if Key was making a conscious nod to the George Carlin joke about a more accurate alcohol health warning label that reads "Will turn you into the same asshole your father was," Tomoya spends the next five years working a dead end job, drinking, smoking, and possibly forgetting his daughter existed. Truth be told i didn't know that a time leap had taken place so when you first see Ushio running around i thought "Oh shit don't tell me Fuko is back..."
Now you get some assorted shit where Tomoya mans up and takes care of the daughter he neglected for five years, forgives his loser father, and makes amends with his in-laws who raised Ushio while Tomoya was spending some quality time with Jack Daniels and the Marlboro Man. Then while things seem to be getting cheery, Ushio walks in, announces that she's constipated, and collapses. At this point i turn to my girlfriend and ask "So wait, five years pass and none of these morons think to have Ushio checked for the same wasting illness that killed her mother?"
To which she replies "If you have time to *****, you have time to make more popcorn. I told you that you wouldn't like the After Story."
To which my dog replied by howling at the ending theme music.
Ushio becomes progressively more ill, and at the point where you think some big miracle is going to happen as Tomoya takes Ushio outside because she couldn't stand staying inside for another moment, she slips into a coma and dies in her fathers arms before they make it to the train station and Tomoya, cradling the corpse of his dead daughter, falls into the snow and likely dies himself.
Before you shout "HOLY SHIT THAT IS DARK," at that point something trippy happens related to the weird little world the series kept visiting consisting of one girl and a trash robot in a post-apocalyptic paradise entering winter where the girl, ALSO DYING, tells her trash robot to gather the orbs of light. At that point, you get an animated "As my life flashes before my eyes and i see all of my deep regrets" scene, then Tomoya wakes up at the point where Nagisa gives birth, only this time she survives and they live happily ever after, Tomoya apparently just having a debilitating nightmare that lasted for half a fucking decade where the only reasons he clung to life died in a futile effort to live one last dream as their own bodies decided "Fuck this shit" and gave out. What i found more depressing was the 180 they pulled which had a fairy tail ending. I would have accepted that the miracle would be that Ushio would be saved, i would have accepted that it became canon for Tomoya to never date Nagisa and instead develop a gay relationship with Sunohara, i would have accepted Tomoya brainwashing Sunohara's sister into being his sex slave, but suddenly the last five years never happened and every bit of realism is hit with a hydrogen bomb?
That depressed me. This might sound psychotic, but i preferred the ending where Ushio and Tomoya died in the snow alone. It was a break away from the bullshit fairy tail endings and it made you feel some form of emotion other than burning hatred or murderous glee. Then it retcons everything and makes things all happy and cheerful and retarded. That shit is more likely to put me on MAOIs than some anonymous little girl and her father slipping into the eternal void of death.