Saikano episode 10 ends with the following message from the subtitlers:

A friendly warning from the team:

This is the end of happiness in Saikano. If you would prefer the anime to have a happy ending consider stopping here and pretending there are no more episodes. Continuing will only bring misery and pain. You have been warned...

Now, this is from a series where there is already a pretty hefty body count. I'm not quite sure how anyone could have been expecting a happy ending from this show. Of course, this just makes me think "You mean it gets more sad?" Once again, as much as I like this show I'm glad there will only be thirteen episodes.