The sickness unto death is what Kierkegaard calls despair, and despair is manifested in form of a young woman named Emiru. Emiru is a beautiful young woman from a rich family and with plenty to aspire to.
Unfortunately, she is consumed with grief. She does not align herself with God or God's plan for her and needs guidance. When she meets a young psychology student named Futaba she gives herself to him. In this way she loses herself to him.
Story by Hikaru Asada and art by Takahiro Seguchi.