Leo Demonheart must prove himself to an elite team of generals in order to officially work for Echidna, the demon queen whom he defeated in the interest of ungrateful human beings.
Leo implements an efficient and collaborative system to make an arduous task easier for Shutina. She is impressed, but not enough to reward him with what he wants.
Leo identifies the flaws in Lili's work and the factors responsible for a slow-moving supply line. He subsequently puts her through a challenge to enhance her abilities.
Disguised as Black Knight Onyx, Leo joins Echidna for dinner and asks her whatever he wants to know; Shutina and Lili prevent Leo from doing something unwise.
Leo tries to enhance Mernes's communication skills by putting him through some tricky challenges; Mernes seeks the answer to a question that has been bugging him ever since Leo joined Echidna.
Leo's past does not affect Shutina and Lili's faith in him; with some help from Leo, Edvard realizes where he is going wrong with the soldiers' training.
Leo confides in Echidna about his tricky programming and its potential consequences; Echidna and the generals learn that only Leo's heart can save the demon world.
Leo recalls how he started to turn from a hero into a destroyer and wanted Echidna to stop him, but Echidna believes that Leo does not deserve a dishonorable death.
Echidna makes an unexpected decision that could change everything for a dying Leo. Shutina suggests a clever way to eliminate the element responsible for pushing Leo to the verge of death.
