There is an alternate ending *SPOILERS*
I know I've already started a topic about how bad this made me feel..but I spend a lot of time of finding a short OVA series called "The Next Season". It hasn't been translated yet so you'll have to watch it with subtitles. IMO this ending is way more depressing than the original. If you wanna see for yourself what happened, read no further.
In this one Narumi and Haruka come together. Mitsuki leaves down, cause her heart is broken. They stay together for a while and do things, and as time goes by Haruka realizes how much her boyfriend has changed. And if any of you remember the scene where he felt asleep on the train in the very first episodes..this kinda happens again, only that she falls asleep and he is wide awake. The end of the story is, that they meet at that tree on the hill where they had their first date..and she breaks up with him, because he has changed so much and she had no chance to grow more mature with him.