Ryoujirou Shiba (柴 遼次郎, Shiba Ryōjirō) is the one who proposed the idea of the Quinx. Addressed as Dr. Shiba, he is in charge of monitoring the Rc levels of the Quinx Squad's members and ensuring they do not reach dangerous levels.
He is an old man who appears to be in his late 60s. He seems to have no eyebrows and sports thin lazy eyes. He has a thick, gruffy mustache, and wears glasses with oblong lenses.
He is shown to be quite serious and professional in his work. He is also extra careful to not offend others and be polite when he speaks, shown when he corrects himself when he nearly calls Saiko Yonebayashi "fat" or when he apologizes for speaking about ghoul biology in front of Haise Sasaki. He does express some form of curiosity.
Dr. Shiba was in charge of the Quinx Squad's routine medical examinations. Sasaki later visited the medical office and chatted with Shiba, who was reviewing the Rc cell levels of the Quinx Squad. Shiba explained if their Rc level are too high, they may not be able to eat human food anymore. There was a discussion between Sasaki and Shiba about Tooru Mutsuki, on whether or not he was capable of being a member of the Quinx Squad.
Shiba was later with Urie in his office with the latter asking for his kagune to be enhanced so he could become stronger. However, Shiba explained the biology of the Quinx to Urie. He advised it would not be a good recommendation for Urie to strengthen his kagune, for the kakuhou might go over its limits.
Urie remembers a conversation with Shiba where he explains how RC cell vessels extend further across the body when One-Eyed Ghouls regenerate. He concludes that because of this, the more Quinx and Half-Ghouls are injured, the stronger they become.
In the past, Shiba discussed the Rc cell levels of the new Quinx Squad with Urie. He noted the levels for the other members were stable but warned Urie his level was nearly double the standard which made him a ghoul according to scientific knowledge of Rc cell levels. Urie responded the frame release surgery was the reason for his abnormal increase. Shiba noted he had confronted kakuja ghouls twice, with Noro being the first and that investigators with the rank of Special Class have engaged a kakuja ghoul in their careers.
Shiba stated his opinion that Urie could ascend to Special Class. However, he requested Urie to try to eat the sandwiches he prepared for their meeting and Urie stated their smell was horrible. Shiba warned him not to go beyond the third frame since he will not be able to return to normal after Urie spat the food out. Urie mentioned Shiba failed to state what Tooru's Rc cell level was at this point. Shiba was briefly quiet and then informed him.
Powers and Abilities
He possesses a sufficient amount of knowledge about ghouls which is enough to be able to perform the Quinx surgery.
Shiba and Haise share a professional relationship with the former considering him objectively without judging his species. Shiba showed curiosity in what it is like for Haise to live like a ghoul with his high Rc cells level.
Shiba expressed concern about Urie's well-being when the Quinx requested the release of additional frames. Urie, however, views Shiba's concerns as superficial and believes the doctor is solely interested in praise for his research and does not actually care about the experimental subjects.
Shiba expressed concern about Tooru's fear of blood questioning if he is capable of being a ghoul investigator. Tooru agrees with this sentiment but insists on continuing. He also seems comfortable enough to tell Shiba about his comrades' issues and conveying messages from Shiba to visit the medical office for their daily checkups.
Shiba was never seen interacting with Shirazu when he was alive, but he was concerned about him in his capacity as a doctor. He noted Shirazu had the most high Rc cells level of the four Quinx and warned Haise not to allow him to utilize his Ghoul abilities recklessly or he will begin to manifest the natural weakness of being unable to consume human food.
Shiba has not been seen interacting with Saiko, but he was concerned about her in his capacity as a doctor. Shiba advises Haise to warn Saiko of her weight increase and having the third highest Rc cells level of the four Quinx.