Shin Ka is a kind doctor and the adoptive parent of Eigetsu Tou. Shin Ka appears to be around the same age as Shouka. Shin Ka is a man from a clan who specialized in healing and medicine. Shin Ka was a kind man who cared deeply about any living being with all his heart. Eigetsu says that Shin Ka was the man who taught him to always smile when he is not sad. Even if people stole from his medicine cabinet, Shin Ka would smile gently and say that he was glad that the medicine would be used to help another person in need. He would also laugh when there was no food left and say that this lack would give a reason for he and Eigestu to go foraging for wild vegetables.
He is able to even touch Yougetsu with his kindness and acceptance of him even though each time he appeared, Yougetsu would be reducing Eigetsu's life. In the past, when Shin Ka found a dying Eigetsu, he tried to save the boy but was unsuccessful. However, as it happened, the White Immortal was nearby and gave Eigetsu life on a whim to see what the boy would do with his limited time left. Shin Ka thanks Yougetsu and makes a lasting impression with the celestial being who was known, up until then, to be an extremely capricious individual. As Yougetsu had come to also love the doctor much as Eigetsu did for his kindness, he agrees to give Shin Ka half of Eigetsu's remaining life when the doctor is killed by a spreading plague which killed everyone in his and Eigetsu's village. After that time had been used up, Shin Ka rushes to the Koku governor and gives him his books on his clan's medicinal knowledge including how to cure the plague occurring in Sa province. Shortly afterwards, he dies peacefully while thinking that he had accomplished his journey and was now waiting for Eigetsu. His writings later prove to be invaluable and vital to curing the Plague.
In the light novels, it is revealed that Shouka had once met with Shin Ka and had seen him as a boy who always smiled and was willing to help people. This meeting made Shouka remark at how different he was in comparison to Shin Ka as while his hands were stained with the blood of hundreds, Shin Ka would be out there trying his best to save people.
