I’m so very normal about Silentclad (and here are a few of my reasons why)
I like to think about how they quietly take care of each other, how they feel most comfortable being together in silence. They let each other exist without question and not long after they meet they quickly begin to feel safe around each other because of this
Also how they have an unspoken bond of trust and can synchronize well together in combat. Ironclad makes the enemy more vulnerable enabling Silent to do more damage and Silent weakens the enemy making it easier for Clad to effectively defend from enemy attacks — they help make up for each other’s weaknesses (they help each other/synchronize in other ways too but this is one of the ways that comes to mind for me)
They both have a lot of trauma, terrible self-esteem, and a lot of self-hatred (Ironclad feels that he’s not worthy because of his demonic side + his loss of humanity and self-control due to the contract with Vakuu and Silent feels she’s not worthy because the years of constantly being belittled by her older sisters have made her feel like a weak burden who will never be enough) but I like to think they believe wholeheartedly in each other. Like Clad sees how strong Silent is in her own way — she’s extremely dependable and has saved his ass more times than he can count because of her agility and quick reflexes helping him dodge some rapid-fire attacks, and Silent sees the human that Clad wants to be and senses the deep feelings and pain he harbors inside even though outwardly he seems like a very cold, unfeeling killing machine. They're gentle with the darkest parts of the other person in a way that they aren't to themselves
Despite that though, Silent was very anxious the first time she met Clad on the climb. She’s very much a lone wolf and prefers to rely on herself so she isn’t a burden to others like she was with her sisters, and even after working with Clad for a while she still worries a lot that she’s holding him back in some way. Clad was also anxious because of his ties to Vakuu — I feel like by the time of the events of STS2 he’s a mix of being half in control of himself and half-consumed by Vakuu dictating/haunting his thoughts to the point where he’s sort of in a mindless, rage-filled haze that makes it hard for him to think properly most of the time. He doesn’t remember much when Vakuu is fully in control but he does remember the feeling of dread he felt when he regained control of himself and realized that he had slain his own comrades due to signing Vakuu’s contract, so he’s scared of somehow turning on Silent or visibly showing the ugly demonic side of himself to her.
But even when there is an incident (at least in my planned fic with them) where that ugly side of him comes out, Silent doesn’t see him any differently. In fact, she sees him as stronger for wanting to try to be human even with the demons living inside him. It makes her want to try to believe in herself more even though she struggles a lot with the nagging desire to gain her sisters’ approval at all costs and the crippling perfectionism she’s developed because of her self-perceived lack of ability. It sort of moves her to try to battle her own demons and to listen to herself and what she truly wants more often instead of the ever-judging voices of her sisters that haunt her (even though she’s been long estranged from them, she still wants to be good enough because they’re the only family she’s ever known and she doesn’t know any different). They both struggle with owning their autonomy — Clad because of Vakuu lurking in his mind ever since he had signed the contract and Silent because she struggles a lot with letting go of her sisters’ impossible standards and living/hunting for the things that satisfy her and make her feel happy instead of what she thinks they would approve of.
I also have a headcanon that Silent is capable of speaking (I like to think that when she speaks it’s mostly to herself and in the company of the moon, because she’s always been lonely and she finds a friendly comfort in the moon — it’s the first thing she seeks after all when she slayed the Heart during the events of STS1) BUT because of “to speak is weak” being so thoroughly drilled in her by her sisters not long after she had learned to speak, she only ever uses her voice to speak with those she trusts deeply and in private. She also has a hard time expressing herself verbally due to this. So when she does finally speak, it's really special. To me Clad is the first one that really hears her voice, he admires that she trusts him enough to be vulnerable with him in that way…
They still really enjoy silence with each other though, and Silent always appreciates that Clad never forces her to speak even after she begins trusting him enough to talk occasionally because it’s easier and much more natural for her to communicate non-verbally. He seems to understand her in a way that no one else can and I like to think their love language is based on touch rather than words. To me they’re not very flashy or showy with their affection but I feel like to the other slayers [Defect, Regent, and Necro] they meet it’s very evident just how much they care for each other. I don't think they fall for each other right away, but they have a very slow burn type of romance and an affection that builds up so slowly and gradually that they don't even realize they've fallen for each other. They like to insist they're just friends but the other three know they have something much more special and passionate simmering just beneath the surface.