Komui Lee is the Supervisor of the Black Order, and Lenalee's older brother. He is Chinese and about 29 years old. His parents were killed by Akuma when they were young, and when it was found out that Lenalee was compatible with an Innocence she was taken away from him. It was shown that Lenalee was kept in the Black Order, away from her only living family (Komui), against her will. When she tried to run away, she had to be strapped down to the bed. However, Komui joined the Order and became the Science Department Supervisor for her sake and Lenalee began to feel more at home in the Order.
Komui is shown as a very whimsical and goofy character, he is somewhat sadistic and borderline maniacal sometimes ("Why did Komui end up so strange...? I patterned this character after Yoshida. My editor."—Quote from Vol 1, Komui's profile page). He drinks coffee nonstop (or more specifically Lenalee's coffee unless he has no choice), is lazy and often tries to worm his way out of doing work by either running away from the office (Reever has to track him down), talking on the phone non-stop even when the other side hung up or other methods (he created several robot named Komurin that went berserk and nearly tore the Headquarter apart). He keeps a notoriously messy desk and lost Allen's letter of recommendation from General Cross when Allen first joined the Order, which led the Order into believing that Allen was an intruder. In the manga when it was asked how much do his colleagues trust Komui, the mangaka answered that it was 99% trust and 1% murderous intent. During his naps, one of the only ways to wake him up is to say that Lenalee is getting married due to his doting personality and due to his "sister complex". An odd recurring theme throughout the series is a small rabbit on his coffee cup, the same rabbit which is seen near the beginning of the series in a costume, and as small flying death blades made by Komui.
Komui, despite everything, does have a serious side. He feels guilty for throwing the Exorcists and Finders into danger, and tries to help in anyway he can, such as making better uniforms to protect the Exorcists. He is also the one to repair damages done to the Innocence of the Exorcists although the method seems very painful. He showed a more solemn and ruthless side in the funeral for the Exorcists and Finders by refusing requests to send the body of the Leader of one of the Finder's teams back to his hometown. He said that all bodies must be cremated in the order. Firm in his beliefs, Komui has shown a daring side in refusing to follow Special Auditor Malcolm Rouvelier's orders about keeping the Akuma Egg, and instead issues his own orders for the Egg's destruction.
Lenalee and Komui seem to share some kind of telepathic link, shown when Komui collapsed when Lenalee was being drowned by Eshi and that Lenalee can tell when Komui is taking a nap even from the other side of the world. He seems to be close friends with the cook Jerry and often hides out in the kitchen.
During an outbreak of a virus he created, Komui, Lenalee and another member of the science department were tied up by Reever, who was possessed by a ghost, who caused the outbreak. The ghost had Reever hold a knife to his throat as to threaten Komui to discontinue the HQ's move. It was eventually shown that the ghost was the collective spirits of all the test subjects used for the Innocence compatibility carried out in the Order and was afraid that it would be left behind alone forever, since it cannot even remember its own name. Komui calmed the ghost by reciting the name of each and every test subjects ever sacrificed, then promised that he will never forget or leave them, since as the supervisor it was his burden to carry their names and lives with him forever.