Overview:
The fourth season of High School DxD.Issei and the 2nd years attend a class trip to Kyoto for well-deserved relaxation, leaving the senior and junior class students of the Gremory family behind. However, once there, they fall under attack and must win without Rias or their other powerhouses.(Source: Anime News Network)
Includes episode 0, Taiikukan-ura no Holy.