Find a Book, Be Recognized by the Thirteenth Master as a Foster Sister, and Deliver a Message for the Fourth Brother During the Confinement Period

At the beginning, she joked about having sex, but she didn't care. When Thirteen was banned, the heroine got in through the hole in the wall. Later, she sent a message to the Fourth and Thirteen, and entered the Fourth's harem. There must be a system to quickly pass through the story.