The Deciding Battle of the Strongest Youth, Begins!
The Rating Game is about to start, but Issei has things to figure out. He has formulated a guess as to why Rias is acting the way she is, but does he dare believe it? His girls give him courage. And, finally, their team steps out into the battlefield.
Aired 12/06/2018EP 10 - The Deciding Battle of the Strongest Youth, Begins!

2018
High School DxD HERO
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)
Note: Includes episode 0, Taiikukan-ura no Holy.