How long did this Japanese film take?

Weeks to months. The shooting process of Japanese films includes film planning, script creation, photography, soundtrack and so on. For an independent film, it takes only a few weeks to shoot, while for a large film, it takes several months. The shooting cycle of Japanese films will also be affected by the conditions and techniques of film production, and the shooting cycle of films that require special effects processing, animation production and other techniques will be longer.