Beatrice and Rem's Cumbersome Cleaning is a shop exclusive limited edition short story. This was later adapted and included in the Re:Zero Ootsuka Shinichirou Art Works Re:BOX.
Rem enters the forbidden library and sees a Beatrice that is holding a bucket and looks quite surprised at Rem's arrival. Rem proceeds to say to Beatrice to give her best while learning how to sing, mentioning that Emilia has improved quite a lot recently after her previous failed attempt, Beatrice angrily replies that it was not the case at all as she merely grabbed it to clean the library (a very possible lie as Rem noticed the bucket had no water in it). Rem then takes the opportunity to clean the library and teach Beatrice how to effectively do it while at it. As Rem cleans the Library, Beatrice asks to join as well since she doesn't want to only listen and want to help as well, soon attempting to clean a bookshelf and ripping an old book apart due to her careless cleaning. The story ends with Rem scolding Beatrice harshly for it and Beatrice lamenting that being treated like that in the end only happened due to Subaru's fault. This story has ties to Emilia and Ram's Very Bumpy Master-Servant Relationship as the idea for using buckets over one's head was first brought up by Subaru to improve singing.