thinking about jeanne and vanitas and their similarities once again..
both jeanne and vanitas were stripped of their personhood and autonomy and used as tools when they were very young—just a means to an end. they don't get to have a choice in what happens to them.
even at the prospect of choice and freedom, they both hesitate to take it because someone else may get hurt. they can accept harm to themselves, they can take getting devalued for the sake of another, but they cannot accept someone else suffering in their stead.
vanitas stares with this gentle expression here, because he knows. he understands the position jeanne was in here probably more than anyone else had understood her before.
when luna enters his life, vanitas is finally given a choice. he can escape without condemning anyone else. he is finally given the opportunity to make a decision for himself. and it shocks him!!
he can't comprehend why he would call for help, because he couldn't before. it's similar to the later scene where he's calling out for his mother in his sleep, but he says that must be impossible, because his mother died during childbirth. he never would have had the option to call out for her, even if he wanted to.
vanitas is a character that desperately wished for help, but did not believe he could ever get it. so he tries to convince himself he could never deserve it, which is part of why when another character calls him kind or shows him love, he feels repulsed by it.
but here, he looks at jeanne, a person who is strikingly similar to himself (whether he recognizes this consciously or not), and he gives her a choice. he offers to accept all of her, even her darkest emotions. even when he struggles to accept himself in this same way. and he gives her the opportunity to ask for help—something he desperately wanted, too.
their relationship may have started off terribly, but they've grown so much since the beginning in their understanding of themselves and one another.
i think that in a way, when vanitas extends to jeanne the option of choice—the ability to call out for help—he's saving a part of himself, too.