Prior to his arrival in the Borderlands, Chishiya worked as a junior doctor with a job at Sakurazawa University Hospital (unlike in the manga, where he was revealed to be a medical student), his practice being within pediatric cardiovascular surgery. It was shown through a flashback that he had a patient named Hayato. Chishiya was seen comforting the boy and then reassuring his mother that his condition was more stable and his surgery would be happening the following week.
Afterwards, a superior took Chishiya aside to inform him that Hayato's surgery would have to be postponed, because the organ transplant waiting list order had changed. Handing Chishiya an envelope containing a patient referral, the other doctor explained that the transplant (originally intended for Hayato) would instead go to the grandson of a friend of the hospital director, a major financial donor. When Chishiya asked about Hayato, his superior said that the boy would get a transplant later, and that Chishiya would have to deliver this news to Hayato and his family.
After Hayato's death, Chishiya's superior attempted to justify the decision by claiming that, even if the surgery had proceeded as scheduled, there was no guarantee it would have been effective. He further stated that doctors cannot always work by their own ideals, and that money, power, and connections often affect the outcome. That was a moment that sent Chishiya down the path of becoming cynical and disillusioned by the injustices within the medical system. He realized that he would not always be permitted to live up to his own ideals, and that his most vulnerable patients would pay the price. The brief flashback also showed a softer, caring side of Chishiya, as he was once hopeful of helping other people.