She Holds an Umbrella for Me, and I Summon Her Soul

I died, in a doomed car accident. In this collapsing underworld where sorrow has become a sea and obsession has become a continent, an ethereal and morbid voice sounded in my soul. "I found you, my Lord of the Underworld..." She is my magic weapon "Red Kite" and the only thing that helps me survive. She holds an umbrella for me and protects me from being overwhelmed by endless negative emotions. She taught me to fight, to devour the walking tragedies and loopholes of the law, promising that this was the only way for us to return to the world. I believed her. Until I discovered that the power she bestowed upon me was contaminating my mind; the "go home" she spoke of was asking me to abandon my humanity, completely merge with her, and regain the position of the lonely and cold old god. She loves me, so she wants to turn the entire underworld into a gorgeous cage to imprison me.