Chibi-Usa is the last survivor of the Moon family and Devon is more than happy that he posseses the daughter of the past realm deceased Champion, Sailor Moon. She too suffers from lost memories and Devon quickly takes the opportunity to manipulate her mind for his gain. Recalling the final battle of the last Century Devon wants Chibi-Usa to turn into her evil adult version ,.. Black Lady (nicknamed Wicked Lady) so she can fight and defeat Elsa and Azula.
But he doesn't want to spend time with the child. Not even when she's fully grown. So he assigns Jack Frost to become her Guardian. Since he was once a guardian it all comes natural to Jack when interacting with Chibi-Usa that eventually the two form a friendship. By the time Chibi-Usa is transform into her evil adult form she falls in love with him. As Jack Frost is still hurting from Elsa rejecting him, He allows Black Lady to make him into the object of her affections.
Turns out it was the second perfect match set up by Devon (His first was Jack & Elsa... Yes, He created it) as Jack finds a perfect soul mate in Black Lady. Together they both share the same feelings of betrayal and hatred toward their enemies .. especially towards Elsa, Anna, Blue, Azula, Elizabeth and the Pines Twins. Black Lady soon starts to target Elsa and the Twins as she strongly believes that Arendelle coming into existence and Ford's Portal ended up destroying her realm.
While Jack still wants to capture Elsa is first concern is Black Lady's safety. As the other villians only care for themselves and Devon at best sees Chibi-Usa as an expensive weapon than a actual human. He even starts to question his desire for Elsa and if she's actually worth the fight, as his love for Black Lady is turning real.
Also both are no strangers to weird love. Jack is a 300 year old ghost with the body of 13 year old crushing on Elsa (21) who should be a minor by comparison as he stalk Elsa since she was a toddler. Chibi-Usa (a 6 year old child transform into a 20's woman) on the other hand kissed her own dad. So the two are perfect for each other as they even have the same weird bizarre love for people. www.youtube.com/watch?v=gy9lrV…