Donten ni Warau Gaiden: Ketsubetsu, Yamainu no Chikai
English title: Donten: Laughing Under the Clouds - Gaiden: Chapter 1 - One Year After the Battle
Japanese title: 曇天に笑う＜外伝＞ ～決別、犲の誓い～
Type: Movie
Episodes: 1
Source: Manga
Genres: Action, Supernatural
Studios: Wit Studio
Producers: Production I.G, Shochiku, Blade, Kinoshita Management
Duration: 50 min
Rating: PG-13 - Teens 13 or older

One year has passed after the great battle against the "Orochi" (gigantic snake). Tenka had been paralyzed from the final battle and he took part of the government's human experiment before the battle. Tenka withdrew himself from society, but his younger brothers, Soramaru and Chuutaro, find out the secret past about their older brother.

(Source: Amazon Prime Video)