I've been struggling to place what the author was doing with Sulfur for a long time, but now I get it and I'm even more in awe of this story.
So I really like how coming to terms with herself has taken away some of Sulfur's jagged edge. She always seemed scrappy, bad-tempered, and like she was kind of burning herself up just being around. She seemed really distant even from her own team, like their earnestness and good-natured outlook ran up against her. She had so much aggression and anger, and it was just constantly leaking out of her.
But look at how she changes when she fully embraces her competitiveness and drive to fight. Her scrappy nature becomes very focused on the actual fighting, and the joy and liberation of it, and so she has room to let her allies get closer, and to be more emotionally connected to them.
The same way Azul's love of pain muddled her ability to fight for victory and her beliefs, Sulfur's love of conflict made it difficult for her to connect with people. And in both cases, embracing the deeper truth of that part of themself let them tap into it in a beautiful and directed way that is healthy and productive rather than maladaptive or destructive. I was having a hard time figuring out how Sulfur fit this story thematically, because she doesn't seem very kinky or sexual about any of this, but now I get it. Her arc speaks to something that lies at the heart of BDSM, a part this isn't even necessarily sexual.
See, when you set aside all the fun things that stand out to people--the bondage, the power exchange, pain play, all that kind of stuff--at its core it's about reaching deep into your heart and letting out all the dark and scary things there in a safe and healthy way. Maybe you have trauma of guilt, and messing up in a scene brings it up all the way up to your skin, and being punished and forgiven absolves you and gives you deep relief. Or you've been forced to bottle up pain and smother your anger for the sake of your own safety, and the chance to be the one in control, to satisfy that urge to hurt someone with a partner who enjoys it and encourages it, burns away at the sense of helplessness you've been carrying, and provides relief for the anger you've had to turn in toward yourself. And you'll notice that the emotions I've described aren't inherently sexual. Indeed, many professional dominants have strict no-sex rules, and are in the business of providing their clients catharsis through their expertise; it's about an emotional release, not a physical one.
All this is to say that while BDSM can be very sexy, the sex is not required. Strong emotions can make sex better, but you don't need the sex.
So, bringing it all back to Sulfur. We don't know her full backstory, but it's clear that some form of anger, which she's had to suppress as a member of society and as a high-profile magical girl, has been festering inside her. But through their scene together, through challenging her and goading her and creating space for her, Baiser dig deep to the bottom of that desire to fight with everything she has and win, to be strong enough, and bring it fully to the surface. She helps her find emotional release and actualization, and that is what the La Verita form is.
It's not sexual, and in being non-sexual it demonstrates the depth of the author's understanding of BDSM as a form of communication and a means for emotional growth. It's another of the many ways that each character in this story showcases all the aspects of BDSM through the archetypes of a mahou shoujo story and I am so here for it.
As a side note, this all makes me even more excited to see what happens with Magenta, who has a strong sense of empathy and willingness to go with the flow, but seems to be kind of a pushover not fully committed to fighting. This story is bonkers.