This is what we called "Real concept of manner movie". They made the whole thing , from this manner to the ending of the movie. Simply love the art! For those of you that don't know, a manner movie (or manners animation) is a short animatic of what is shown in the cinema right before the movie, telling you the rules you must abide by whilst there. This includes turning your phone off/putting it on silent, no conversations, no fire or weapons and other factors included to match the style of the movie. In this case, we are being told this by Sora and Shiiro,who display their own characteristics before presenting this movie to you. We also see Jibril and Steph showing their personalities and representing what you should not do, and getting scolded by the siblings.