LINK’S DEMEANOR : grows more melancholic & cold the longer he is awake following his reawakening in the Shrine of Resurrection. Zelda herself notes that prior to the Calamity, Link as a person had steadily grown more and more distant over the years training & preparing for his role as the Champion of Hyrule and although Mipha once stated she still sees the carefree & loving person buried inside him he had once been as a child, the gravity of his destiny and the expectations of those around him had systematically broken down how lighthearted he had once been while growing up. He felt the burdens were too heavy, but they alone were his to bear, so he didn’t ask for help. His father, also a knight guard, was ecstatic and proud when his son was identified as Hyrule’s Champion, reborn to meet Ganon in combat once more, but Link himself never felt he was up to the task and often floundered with his duties, wracked with guilt that he wasn’t good enough. He didn’t want to disappoint those who were relying on him, and so she shouldered it all on his own. He’s always suffered from imposter syndrome when it came to his role as Zelda’s champion, something he never quite learned how to handle before he was fatally injured and left to sleep for a hundred years as Zelda continued the fight on her own.
When he wakes up, he has no memories of his past. Not his failure to save Hyrule, not all that he’d lost, not even the pressure he’d felt from an entire nation to carry the world’s future on his shoulders. At the start of BOTW’s storyline, he is far more carefree and expressive. He smiles more, he has more energy, he has an appetite for adventure. But the more he travels, the more he remembers. And the more he remembers, the more that pressure grows on his shoulders once more. He starts to smile less. He withdraws into himself, relying more heavily on sign language even with those who don’t understand it, resorting to him communicating through written word or body language instead of speaking. He grows more solemn, contemplative. Part of him begins to question what the purpose of his survival was : he should have been the one to die, not the other champions. It was him who had failed, back then. He becomes haunted by survivor’s guilt, as well as the weight of his past failures and what it did to Hyrule. Those thoughts come back that he isn’t good enough, but he pushes forward regardless because Zelda is waiting for him and no one else can do it.
Link is incredibly strong, but he also tends to bear his burdens on his own. He does not vent his troubles, nor does he seek help. He takes his destiny and follows it like a written in stone guideline, because he believes that every other incarnation of Link has fulfilled their destiny on their own. But he feels disconnected from that, from who he should be. He does not feel like a hero, he feels like a blank slate that everyone projects their idea of who Link should be onto. The heroic deeds they sing of are not his. The one duty that was his, he was not strong enough to fulfil.
In short, he is more expressive than he used to be. He has more of a sense of humor and can be more interactive, but that bubbly persona of his slowly starts to die again, little by little, as history repeats itself and he’s forced to once again wear the image of Hyrule’s Champion : a role he does not feel he deserves, and now, one he feels like he has tainted.