Ferdibertgard: How would intimacy with Hegemon-form Edelgard work? How would they make her not feel monstrous?
Edelsythea: The game dances around the Crest experiments. Have them help each other through night terrors brought upon by memories of what was inflicted, and you don't have to shy away from descriptions of what they may have been forced to endure.
Lysithea/Hubert: Hubert and Lysithea put into practice the 'ancient techniques' that were discovered after defeating Those Who Slither in an attempt to restore her lifespan. Anything the Slithers are involved in tends to be gruesome, and Hubert would never let anything be applied to Lady Edelgard without rigorous testing first.
Claurenz: Claude wasn't raised neck-deep in Crest Culture, and his mother was rather cagey about the effects of having a Crest, so when Weird Things start happening to his body, he goes to Lorenz for clarification, and finds out uncomfortable truths.
Ferdirenz: The first manifestation of a child's Crest confirming what blood tests indicated was always a cause for celebration--Lorenz and Ferdinand have their first manifestation on the same day, together, and no one warned them how much it would hurt, among other...changes.
More generally, Crest nonsense getting freaky and weird and Uncomfortable.
DimiMari: Rumors of the Queen's disappearance have caused concern; no one would have expected that the 'captured' Demonic Beast currently residing in the palace dungeons was her, nor that Dimitri still held out hope his love would one day return to him.
Sylvain/Mercedes: Sylvain loves all his children, even the ones without Crests. He strives to be a better father than his father was, and in doing so, has to come to terms with the abuse, neglect, and harm he long normalized. Mercedes helps him through this process, particularly when he injures himself as he rages against the injustice of it all
Dimivain: Both men see themselves as monsters. Perhaps it takes one to know one. That it why, only when they are alone with each other, that they feel safe enough to shed the trappings of humanity.
Dimilix: Dimivain still dreams of ghosts and the dead. Felix helps him through the nightmares and hallucinations.
Sylvix: Sylvain lives and fights like he wants to die. Felix wants all of his friends to survive. These two drives clash.