Otonashi Hatsune is Yuzuru's younger sister. She was diagnosed with cancer and has been bedridden for two years. Within this period, Yuzuru acts as her guardian, usually visiting her to give her manga to read and to keep her company. Compared to her brother, Hatsune enjoys studying and couldn't wait to start school. However, her sickness kept her from going outside. [From Angel Beats! Wikia]