Donten ni Warau Gaiden: Ketsubetsu, Yamainu no Chikai

The first part in an anime film trilogy adaptation of the Donten ni Warau Gaiden spinoff manga.
One year has passed since the great battle against the "Orochi" which left Tenka Kumou paralyzed from the waist down. While some of the old squad has remained together, Tenka has isolated himself. As his brothers, Sousei, and Kiiko try to reach out to him, hidden details are revealed from Tenka's past.
(Source: Eleven Arts)