The Nishikata exclave of Ōno domain was located in Niu County, about 30 kilometers west of Ōno domain's castle town in the hill country between Echizen’s lowland corridor and the Sea of Japan. Two of its twelve villages bordered directly on the coast. In 1850, Ōno domain established a rural intendant’s (daikan) office in Nishikata because the exclave had become increasingly important for the domain’s responsibilities in coastal defense. The intendant’s office was placed in the fief’s main village—Ota, a rural center of about 1,000 inhabitants. The people of Nishikata had few social ties with fellow subjects in the core part of Ōno's domain territory. Their villages and other kinds of occupation-based status associations were not usually integrated with those in Ōno proper.

It is unclear whether and when Ōno’s vaccinators attempted to bring the vaccine to Nishikata. But their colleagues in the vaccinators’ association of Echizen certainly deemed Ōno's vaccinators responsible for vaccination-related matters within that exclave. Kasahara Ryōsaku had two separate exchanges with Ōno's domain physicians Nakamura Taisuke and Hayashi Unkei that clarified his expectations regarding Nishikata, and his thoughts about the relationship between domain rule and the vaccinators' association more generally. The first of these exchanges dates to 1853.

For background on territorial fragmentation in Echizen province, see The Territoriality of Warrior Rule.