The older brother in the movie is lucky to have a younger sister, Tachibana, who is not only obedient and gentle but also understands his psychology very well. Because his parents died early, he had to spend his youth alone to raise his little sister until she became an adult, so she sympathized with what her brother was having to endure, especially his suffering. Suppress your own physiological needs. For this reason, every time he came home from work stressed and tired, she sympathized and expressed her desire to help relieve him by using her body to make him have moments of sublimation and joy. enjoy being with relatives. What a lustful sister.