Responses
The manga is an adaptation of the movie...there's actually lots of movies that has a manga adaptation after its release (๑•ㅂ•)و✧
So that's how it is eh #－.－)
Most of anime movies don't have manga origin. Mangs are drawn after the movie either by director (like makado) or an other mangaka
Why is the manga being released when we've already got the movie long ago? So you mean this movie had no manga of its own before being made into a movie?