I've thinking about this a lot actually
Like them realising that shadow milk isn't acting like how he would usually and they become worried for his own wellbeing. So they decide to "betray" him for his own good and find someone else who is more mentally stable to help
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The fact that both black sapphire and candy apple are willing to literally get themselves killed/almost killed for shadow milk is so sad to me. Like they genuinely have no regard for their own wellbeing if it means making sure whatever SMC wants or plans succeed
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God bless black sapphire for genuinely constantly asking if shadow milk is actually okay. He’s so worried about shadow milk after hearing what the ultimate dough does to its host ahhh