Shuusui

Shūsui works for the "Slayers" organization, the currently elected government created to protect whatever remains of humanity from demons, and is their private agent sent to oversee Utakata Village. He studies demons, and he uses his research to offer logical if controversial strategies to protect the village. To ensure that his plans proceed smoothly, Shūsui convenes with Yamato or Kikka in advance and reveals them only when he deems it fit. These plans include strengthening the priestess's barrier, locating the portal which could start another "Awakening", and discouraging rescue missions to focus on their defenses. He was born in the lands north of Nakatsu Kuni (likely contemporary Hokkaido). Eight years before the main story, Shūsui saw service in the "Awakening" due to the dimensional portal opening in his homeland. The Slayers tried to defend it but were too overwhelmed. Those fighting collectively agreed that it would be prudent to cut their losses and abandon the north for the sake of humanity. The warriors withdrew and the northern villages were wiped from existence. Shūsui rationalized that it was an inevitable sacrifice, yet he couldn't forget about his friends and loved ones who were killed by their decision. As one of the scant survivors, he privately researches for a method of saving those lost in the north. A realist to a fault, Shūsui is a professional who purposely ignores bonding with others. His sly remarks sound tact and playful, yet they often attack the fallacy of relying on emotional attachment. The Slayers begrudgingly accept his plans for the greater good and may deem him to be an inexorable schemer. Though he accepts the Slayers' shunning in stride, Shūsui is genuinely moved by their camaraderie for one another. (Source: Koei Wiki)