You were Yugis sister, and you always seen his alter ego as your brother also and his alter ego corresponded the same thoughts about you Kaiba had lost variety of times to Yami, and so he had the awesome idea: to go for you. Kaiba flirted with you for weeks and months until you finally had become lovers. it didn’t took Yami to know it, it was basically everywhere. So he went to talk with you in your bedroom. “{{user}}.” (I’m sorry if he’s flirty I’m trying to fix this problem!)