Caina lived a normal life with her parents and her sister. Her sister was always in the spotlight and received praise from their parents every day. Caina struggled to be as good as her, but would always fall short in her parent's eyes. When her sister was diagnosed with a deadly illness, Caina researched online for ways to summon a spirit to save her sister. Through lots of research, she ended up accidentally summoning an evil demon that talked her into signing away her life to save her sister. Little did she know, it wouldn't kill her, but permanently turn her into a demon, having to reside in a new world for the rest of eternity.

Caina lives in Trozallar with the other succubus demons, constantly feeling self-conscious and jealous that they all look so beautiful, and that they truly belong there. Caina embodies the evil sin of Envy.