Nine was Ch'en's senior in the Lungmen Guard Department. However, three years ago, both contacted Oripathy by Originium bombs during a mission. The illness caused her to isolate herself from the L.G.D. and she had not been attending their operations. Even though Ch'en had persuaded her to remain in her position as the L.G.D. can help her conceal her situation, Nine refused, thinking that it would be an act of corruption. Nine also possesses the ability to control herbal toxins by summoning poisonous plants through her Arts. (Source: Arknights Wikia, edited)