Felt-chan's Imprisonment Life (フェルトちゃんの監禁生活) is a shop exclusive limited edition short story. This was later adapted and included in the Re:Zero Ootsuka Shinichirou Art Works Re:BOX.
Felt wakes up at the Astrea Mansion after Reinhard kidnapped her. Felt started talking about why he kidnapped her and Reinhard started explaining the Insignia.
Couple minutes later, Grimm walks in with dresses in his arms and asks Felt if she want's to try it on her. Felt claims that she hates dresses but still tries them as Reinhard talked her over to do so.