After Seeing the Comments, I Got a Happy Ending with the Puppy-Like Guy

Actually, I'm Looking for a Specific Book

The female lead is called Sui Xin, and she took her mother’s surname. The male lead is called Sui Dongsheng, and he also took his mother’s surname, though I’m not sure if that’s the exact name. It’s a short story. It opens with the female lead going to the male lead because she can never find an empty seat at the library. He built her a prison room, and the female lead is reborn.