High School DxD Born OVA

After a series of hard-fought battles, Issei Hyoudou receives a new assignment that has nothing to do with destroying enemies but demands just as much resolve: helping his former rival Riser Phenex, once an arrogant devil who has completely lost his fighting spirit, get back on his feet. To carry out the task, Rias Gremory and her whole household travel to the Underworld, where the Phenex clan's domain lies. Complicating matters, Issei has to turn to the elder dragon Tannin, the legendary being who once trained the Oppai Dragon himself.

Under Tannin's guidance, Issei tries to tap into his own hidden reserves of power while supporting Riser through trials of fire and magic. The training takes place near hot springs where Rias and the other girls are relaxing, so the young devil struggles not only with outside challenges but also with the temptations of thinking about his companions. Riser, stripped of his former pride, is in the middle of an inner crisis and doubts he can ever be who he once was. Gradually a strange kind of respect forms between him and Issei, as the former enemies realize they share the same goal: proving to themselves that defeat is not the end.