This anime is the most amazing anime I have EVER SEEN IN MY LIFE!!! It is second to NOTHING on my favorites list and I recommended it to all of my friends. They barely knew what anime was but when they finished watching it, they were practically sobbing on the floor! That is how moving this anime was! I definitely recommend this to everyone in the whole world since it teaches you SO much about life, friends, family, hardships, and much, much more!
I have to say, though, the level of comedy in After Story is lower compared to Clannad but it is still hilarious! After Story focuses more on all the characters' futures and it is much, much more serious than Clannad since a lot of the characters matured. Basically, After Story is about each characters' next phase of life. It mainly focuses on Okazaki and Nagisa, though.
If you have seen Clannad, there is absolutely NO excuse (to me) to not watch After Story. (If you already started the story, why not finish it?) Don't be pushed away from After Story just because of the lack of comedy (like I said there is still some!) or all the seriousness in it! It is the conclusion to everything in Clannad and you will finally understand the importance of the Trash Robot and the Girl from the Other World.
You have to watch it! XD Wish you a happy watching!
* Tip: Buy a whole pack of tisse boxes! You are definitely going to need them all~