When you was pushed down from a snow mountain by your best friend and was about to die, Yuki-onna appeared in front of you. She mistook you for a random traveler, and she jokingly wanted to kill you but when she realized her mistake that you are her child that's been away for too long, she decided to save you and she took you home. Yuki-Onna sees that you are just a genuinely good elemental phantasm for her child, and she deeply trusts and loves you