Series: Caged Maricha / 籠の中のまりちゃ (kopmoti)

Maricha is an ex-stray who is kept captive by Oniisan, an expert abyuser who made sure that Maricha's life is a living hell that she can never escape from. Before her kidnapping, Maricha lived happily with her mother and ate tasty grass dango everyday. But now she can only dream about going back to those days.

https://www.pixiv.net/en/artworks/101711755
There's a prequel and a sequel to this series but it's locked behind the artist's fanbox :(