REM 0: Knockin' at the Door

REM 0: Knockin' at the Door is the zeroth chapter of Yumekui Merry.

Synopsis
Mr. Tachibana, Isana Tachibana and Yumeji Fujiwara were praying at the grave of Ayumi, the late wife of Tachibana. After finishing, he tells her that he'll be back.

On their way back home, Yumeji apologizes for coming along but he tells him that it was fine since he is like family and Ayumi was glad he was there. Yumeji begins to recall that when he was young that he would go to her for help but then yawned. Tachibana got a bit mad at the yawn and asked Yumeji if he was up for a little one-on-one later which freaked Yumeji out.

Isana asked Yumeji if he stayed up late doing something for his club. He tells her that not only that, also his consciences has been uneasy and wonders if he did anything to make cats angry. As they have this conversation, they walked pass a tree unaware that there was a girl sleeping in it.