Saishuu Heiki Kanojo, School Days Recommendations
While watching both of these anime, I got the same feeling many of the times. Both of the stories start off with a shy girl and a kind of jerk guy getting together, the only thing is that Saikano has more science-fiction elements.
From there, there are quite a few sexual scenes in both of these anime and I got creeped out by some of them in both of the anime. The main guy character in both of these has trouble keeping his mind on one girl at a time, although the one in Saikano is way nicer, but they are both unloyal, sometimes uncaring people.
Depressing as hell. Also, both romances that look like they'll be cheerful and fun for about five minutes (SaiKano) or three episodes (School Days).
They might not appear to be very similar, but the progress of the relationships between the characters in both animes are depressing to say the least.School days and Saikano share the sad storyline and (I don't want to write a spoiler) have pretty endings that get you want to see it again and again. Hope this was helpful