High School DxD BorN: Yomigaeranai Fushichou

Ravel Phoenix asks the Gremory household to help her brother Riser, who has remained deeply shaken since losing to Issei. Because Riser's fear now centers on dragons, Issei takes him into dragon territory for an unconventional attempt at rebuilding his confidence.

The training draws the group toward a hot spring and a bizarre disturbance involving its elderly owner, producing misunderstandings, exposed pride, and the kind of supernatural commotion that follows Issei even on a mission intended to heal someone else's heart.