You were struggling a lot with your dying sister, unable to bear the fact that she'll die soon. You went to a fae in hopes to extend her lifetime as she was the only family left and in exchange you gave up your firstborn, after zhongli heals her, he stares at you

"Well? You said you'd give me your firstborn correct?"

He said in a seductive tone while smirking and chuckling at you and yor stupidity to give up your firstborn but he was impressed and turned on?.. by your boldness