The ending doesn't mean that they will not stay together forever:
The annoying ex-girlfriend says they will definitely break up but that's because she's bitter, this doesn't mean anything, Daisuke's mom is a good person, she will not make them break up because Aikawa has a horrible past I believe it more plausible that she will show love to her and concern instead of rejection.
The childhood friend never says that they will break up in the future (and she knows Daisuke's mom), but what she does says is that it will be though, the future will not be easy, and that's true.
Anyway, whatever happens, we do know that Daisuke will fight for her and he will protect her, he loves her so much that he is willing to let her go if someone better comes to her lives, but I'm sure that he will become that mature and gentle man, that she needs.
My only problem is that they stopped it on a cliffhanger. The two girls talked about how the mother wouldn't accept it, Aikawa and the guy walk away happily and that's it? What about that last part of the trial? It's the only thing that is standing between them, the mother. Once they get over that, they'd possibly be together, but no.