I've Begun My Training!.Rias agreed to fight with Phoenix in ten days time. In the meantime, Issei begins to train in an isolated area under Rias' supervision as they prepare for the rating game. Issei fails in each lesson from everyone and is greatly discouraged. First he loses to Kiba in sword fighting, then he loses to Akeno and Asia in manipulating magic, and finally he loses to Koneko and gets beaten badly as a result. However, in Lesson four, he creates a power through visualizing the breasts of his intended victims. That night, Issei, in a waterfall mausoleum, tells Rias that he admires her as the best mentor for him, however he admits that he isn't useful for her and considers himself as the most useless devil...