LUCID - Young Lily and Koi Yang

On the outside, Koi is a shy and introverted person, but deep inside she is very compassionate and devoted. She rarely goes out and is often found studying. Due to this behavior, classmates think of her as a very cold person. She only has one friend, Lily Silver, who admires her for her passion for studying, duty, and responsibility. Unlike her daring friend Lily, she is very reserved and practical with life. She is also known to be very ambitious.

In Lucid Love, she is Lily's best friend at school. She supports Lily by advising her and  subduing her over extravagant behavior to prevent her from danger. She is also jealous and has academic rivalry with Raven Knight (she used to be top1 before Raven transferred to their class)

In Lucid Eye, she is Illume's personal doctor and participates as a scientist in Black Knight Syndicate's "LUCID" Project. She is known to join BK because Lily felt so alone and depressed in the Black Knight Syndicate. Even though Raven acknowledges Koi Yang's skills as a scientist and a doctor in the syndicate, he cannot help but doubt her loyalty at times.