The second volume of Orange, The Complete Collection still has some emotionally driven stuff to tell, and I admit that my heart has been tugged a few times. But volume two has a narrative that is not as solid and cohesive as the first one. The time jumps are not as organic as they were before. I also felt that the themes of being strong, not giving up and saving a life have been used over and over again that it felt that Orange should have been more effective if it were shorter, yet the ending happened so fast that the story could have used a couple more pages. 
 The ending resolution is exactly the way you have perceived it will end. It's quite a bummer if it ended the other way around. I would also like some reconciliation to happen with the future group, like a grown-up Kakeru showing up in an epilogue chapter fulfilling the wish of the "original" ones . 
 As for the six characters they are all extremely likeable until the end (even though Kakeru is douchey many times and Naho almost got to my nerves for her "Naho-isms"), but the only personalities that have been fleshed out are Naho, Suwa and Kakeru's. 
 There's also a completely different story after the end of Orange. I didn't like it. 
 Orange lives up to its readers expectations. It is warm, heartbreaking at times but most importantly, it is a testament about the good things that life can offer, even at times when one doesn't feel like going on. It is a celebration of friendship, love and happiness.