I care only about putting an end to what I beganAs the game ends, it comes time for the party to battle Van in order to free Lorelei and halt the creation of a world of replicas. While Jade's character and motives remain largely ambiguous (to say the least) to the very end of the game, it's obvious that he wants to stop Van's replica world and most importantly, "take back fomicry." Seeing Van's perversion of replication combined with Luke's struggle to become his own person gave rise to a desire to stop fomicry from being exploited, but not necessarily stopped altogether.
So not only is the final battle a struggle to stop Van's goals, but a struggle against the use of fomicry for negative purposes. Jade had also been to one to command the gathering of replica data from the people of Hod, and if Jade leads the party without Luke or Tear, Van states that, "your replicas advanced research into hyperresonance and caused the destruction of Hod. And at the same time, they have become the way to free the world from the Score." For Jade, the final battle is also a fight against the misuse of multiple things that he was responsible for.
Following Van's defeat, it's left up to Luke to release Lorelei. The party says what they hope aren't goodbyes, and Jade (awkwardly) reveals that he does in fact want Luke to return, for Luke's sake but also for his own as well.
"…that’s why you must come back alive. Or rather, I hope you do."
On Luke's twentieth birthday (presumably two years after fighting Van), the party returns to Tataroo Valley and catches sight of a red haired figure in the field of selenia flowers. And for the first time, we see Jade with what looks like a sincere smile.
i am a terribly cold personAt one point, Guy claims that "Jade will always be Jade." I agree that Jade's interesting personality remained constant to the very end, but I do think he experienced a bit of character growth. Though it was nothing as drastic as the change we saw in Luke, I think that Jade did in fact change, if only a little. First of all, we see a change in the personal feelings that he's willing to express. Simply put, Jade doesn't like to talk about himself. In a serious manner, at least. While the other characters, mainly Luke and Natalia, show their emotions rather clearly, there's no telling what Jade is thinking or feeling during the majority of the storyline. However, by the end of the game Jade does honestly express himself a bit. When hearing that Luke is going to sacrifice himself at the Tower of Rem, Jade tells Luke that he thinks of him as a friend. Luke is a bit surprised, but Jade understands Luke's shock and calls himself "a cold person." He later speaks to Luke about his difficulty understanding life and death and vows out loud to "put an end to what he began" when fighting Van.
But do these actions signify a change in Jade's character? Probably not entirely; while he seems to be a bit more open with his thoughts by the end of the game, many of the things Jade says are things that he had likely already realized. Mainly, the fact that he was responsible for the creation of fomicry. From the start of the story, he expresses anger towards those who were using the forbidden technology. Jade is one quick to recognize where responsibility lies, which is one of the (many) reasons he was so hostile to Luke following Akzeriuth. So given his character, Jade knew that he was at fault for many of the disasters to hit Auldrant. Also, he was no doubt aware of the face that he presented to people, like the fact that he was "cold." I think his thoughts in relation to himself remained largely unchanging during the course of the game. But then again, the willingness to speak his thoughts sincerely is a change in and of itself. So while Jade never actually admits much of anything, he does show some sincerity in expressing his thoughts regarding himself by the end of the story.
I hope that made some sense.
However, at one point Jade tells Luke that, "I've learned a lot of things by watching you." He doesn't specify exactly what, aside from the fact that he lacks Luke's aversion to killing humans. But it's implied that Luke's dealing with being a replica changed Jade's perspective on fomicry and replicas themselves, which I've attempted to detail here.
Like I mention above and in the Luke section, we do see a definite change in Jade's attitude regarding others. Although everyone had their own reasons for partaking in the game's journey, they ulitmately become a unified team. Jade comes to trust Anise, Natalia, Guy, and Tear, not only in terms of battle capability but personally as well. Jade isn't the type of person to stay around people he doesn't like longer than he can help it. He understood the grave threat that Van posed to Auldrant, and I doubt he would have gone about stopping him with people that he didn't trust. The group even returns to Tataroo Valley together on Luke's coming of age day. This marks a big change from the game's beginning, where Jade didn't want to be around characters like Luke and Natalia any longer than he had to. But Jade's perspective changed while the others matured, creating a strange friendship between the unlikely allies.