A volunteer doctor working for the Akatsuki Conglomerate. He is in charge of overseeing the medical examination Nao and his fellow survivors undergo on a regular basis. Educated in the United States, he is affable and highly skilled. The head of research into the Baroque phenomenon. Tonosaka is a psychopath unable to empathise with fellow humans; he sees them as test subjects to be experimented upon. He broke off his engagement with Sabikawa shortly after taking charge of the Baroque project. In order to prove his theories on the Baroque phenomenon, he would go to the extent of hiring the ex-PLA mercenary pair to interfere with the efforts of the Six to secure Yuuri and Nao as well as using them to train up the combat abilities of the nascent Baroque wielders. His amoral nature allows him to carry out otherwise despicable acts such as organised gang rapes and psychological manipulation in the name of research. He dies in one route but survives in the other two.