Ryūji Kōno engages in a brief romantic and physical relationship with Ami Nonomura during her period of emotional vulnerability after her separation from her stepbrother, Hiroshi. He treats Ami primarily as a sexual partner, offering little genuine emotional support or connection. The superficial nature of their dynamic becomes clear to Ami when Kōno makes a pass during a meeting intended for conversation, revealing the transactional essence of their interactions. This realization prompts Ami to end the relationship, concluding Kōno's role in her story. His background, motivations, or development beyond this specific involvement remain outside the narrative focus.