Donten ni Warau Gaiden: Ouka, Tenbou no Kakehashi
English name: Donten: Laughing Under the Clouds - Gaiden: Chapter 3 - Conspiracy of the Military
Genres: Action, Supernatural
Type: Movie, Episodes: 1
Aired: Sep 1, 2018
Studio: Wit Studio
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
The three brothers discover that the human experiment banned after destroying the "Orochi", is still going on to secretly revive the evil snake. They also find out that some ex-members of the Yamainu (the Japanese military unit formed to kill the snake) are behind this conspiracy. The brothers fight together again in a battle against the military.

(Source: Amazon Prime Video)