The reason why Kuranosuke chose Yamashina seems because of the matrimonial and familial ties between the Oishi family and the Konoe family (Nagayuki SHINDO (vassal of the Konoe family), was a relative of Genshiro SHINDO, his uncle on the Oishi side, who was the caretaker).
内蔵助が山科を選んだのは、大石家が近衛家の親族であるとともに、大石家の叔父進藤源四郎の一族進藤長之（近衛家家臣）が管理していた土地だったためと思われる。