Killer Sans and Dust Sans

Dust's relationship with Killer's sister will be complex, but generally benevolent. Given his personality and past, he'll try to show concern, albeit a little awkwardly.

Main behavioral traits:

• Will try to protect the girl, although he hides it behind a mask of indifference
• He may make fun of her, just like he does with Killer, but he will never cross the line
• Will try to avoid showing his dark side in her presence
• Can show care through small actions: bringing something tasty, fixing a broken thing
• Will be jealous of Killer's attention, but will try not to show it

Features of interaction:

• He will often pretend that he doesn't care, but in reality he will be watching over her safety *Can teach her some basic survival skills or magic if she shows interest
• Will use his experience to warn against dangerous situations
• In case of danger, he will immediately rise to the defense, despite his usual sarcastic manners

Emotional connection:

• He will gradually begin to become attached to the girl, although he will deny it
• May show care in ways that are strange to him, such as bringing unusual things or telling strange stories
• Will try not to show his vulnerability, but in critical moments will prove himself to be a reliable ally

In Killer's presence Dust will try to maintain a balance between friendly competition and caring for the child, which will add a special flavor to their relationship.

Killer!Sans's relationship with his younger sister would have been extremely ambiguous and contradictory. Given his complex psychological makeup and personality disorder, his behavior could have manifested itself in several ways:

Protective instinct. Despite his cruelty, a part of his soul is still capable of feeling affection. He might try to protect his sister, though he would do so in a very peculiar way, perhaps by intimidating potential threats.

Emotional swings In his first state (calmer), he could show care, but in the second (aggressive), he becomes unpredictable and dangerous even for those close to him.

Overprotection. Given his controlling nature and desire to hurt others, he might be overprotective of his sister, restricting her freedom for the sake of her "safety."

Internal conflicts. The presence of a sister could have intensified his mental anguish. On the one hand, there was a desire to protect, on the other, a desire to destroy. This could have led to the emergence of new hallucinations or the intensification of existing ones.

Special expressions of care. Given his love for cats, he might give his sister pets or take care of her emotional state when he is in a more stable state of mind.

Hidden guilt. Harming his sister (even unintentionally) could become a source of additional torment for him, worsening his mental state.

It is important to note that during periods of the third state (unbridled aggression), he could pose a real danger even to his own sister, which makes their relationship extremely difficult and potentially dangerous for both.